MECHANICAL  PROCESSES 


AN  ELEMENTARY  OUTLINE  OF 

MECHANICAL  PROCESSES 


GIVING  A  BRIEF  ACCOUNT  OF 

THE  MATERIALS  USED  IN  ENGINEERING  CONSTRUCTION  AND  OF  THE 

ESSENTIAL  FEATURES  IN  THE  METHODS  OF  PRODUCING  THEM, 

ALSO  DESCRIBING  SHOP  PROCESSES  AND  EQUIPMENT 

FOR   THE   SHAPING  OF  METALS   INTO    FORMS 

FOR  ENGINEERING  AND  GENERAL  USES 


ARRANGED  FOR  THE  INSTRUCTION  OF  MIDSHIPMEN  AT  THE  U,  S.  NAVAL  ACADEMY 
AMD  FOR  STUDENTS  IN  GENERAL 


BY 

G.  W.  DANFORTH,  U.  S.  NAVY 

Instructor  in  the  Department  of  Marine  Engineering  and  Naval  Construction 
U.  S.  Naval  Academy,  Annapolis,  Maryland 


ANNAPOLIS,   MARYLAND 
THE  UNITED  STATES  NAVAL  INSTITUTE 

1912 


COPYRIGHT,  1912 
BY 

PHILIP  R.  ALGER 

Secretary  and  Treasurer 
U.S.  Naval  Institute 


Q0<*ftttrtore  ( 

BALTIMORE,  MD.,  U.  S.  A. 


PREFACE 

This  book  is  intended  as  an  elementary  account  of  the  several 
classes  of  processes  employed  in  shaping  materials  of  construction 
for  various  mechanical  uses.  A  brief  account  of  the  properties  of 
these  materials  and  of  the  methods  of  producing  them  is  also  given. 

Effort  has  been  made  to  present  the  subject  matter  in  brief  and 
elementary  form,  with  sufficient  detail  to  outline  methods  and 
principles  clearly.  It  is  intended  to  show  completely,  though 
briefly,  the  steps  of  metal  manufacture  from  the  ore  to  the  finished 
product,  so  that  the  student  may  be  enabled  to  classify  all  branches 
of  metal  manufacture,  and  may  pursue  intelligently  such  study  as 
will  give  fuller  information  than  is  possible  to  include  herein. 

Most  of  the  subject  matter  is  from  notes  taken  by  the  writer 
when  on  engineering  instruction,  on  shipyard  inspection  and  other 
engineering  duty  and  during  recent  visits  to  manufacturing  plants 
where  processes  were  observed  through  the  courtesy  of  officials  of 
those  plants,  and  where  valuable  information  was  obtained  which 
could  not  be  obtained  otherwise.  These  notes  were  in  several  in- 
stances checked  and  supplemented  by  information  from  various 
technical  books  and  papers,  particularly  by  reference  to  their  re- 
ports of  original  investigations.  A  list  of  the  books  of  great  assist- 
ance in  this  work  is  as  follows: 

Iron  (The  Metallurgy  of) — Turner. 

Steel  (The  Metallurgy  of)— Harbord  and  Hall. 

The  Metallurgy  of  Iron  and  Steel — Stoughton. 

Chemistry  of  Materials  of  Engineering— Sexton. 

Elementary  Text  Book  of  Metallurgy — Sexton. 

Materials  of  Engineering — Thurston. 

The  Materials  of  Construction — Johnson. 

Calcareous  Cements — Redgrave  and  Spackman. 

Hawkins  Mechanical  Dictionary. 

Cyclopaedia  of  Mechanical  Engineering. 

Journal  of  the  American  Society  of  Naval  Engineers. 


302099 


4  PREFACE 

The  shops  of  the  following  named  industrial  companies  were  re- 
cently visited : 

Acme  Steel  &  Malleable  Iron  Works,  Buffalo,  N.  Y. 

American  Iron  and  Steel  Mfg.  Co.,  Beading,  Pa. 

American  Sheet  and  Tin  Plate  Co.,  Pittsburgh,  Pa. 

American  Steel  and  Wire  Co.,  Springfield,  Mass. 

American  Welding  Co.,  Carbondale,  Pa. 

Babcock  and  Wilcox  Boiler  Co.,  Bayonne,  N.  J. 

Benedict  and  Burnham  Mfg.  Co.,  Waterbury,  Conn. 

Best  Mfg.  Co.,  Pittsburgh,  Pa. 

Bethlehem  Steel  Co.,  South  Bethlehem,  Pa. 

Billings  and  Spencer  Co.,  Hartford,  Conn. 

E.  W.  Bliss  Co.,  Brooklyn,  N.  Y. 

Brown  &  Sharpe  Mfg.  Co.,  Providence,  R.  I. 

The  Carborundum  Co.,  Niagara  Falls,  N.  Y. 

The  Coe  Brass  Mfg.  Co.,  Ansonia,  Conn. 

Cramp  &  Sons  Ship  and  Engine  Bldg.  Co.,  Philadelphia. 

The  Crosby  Co.,  Buffalo,  N.  Y. 

Fore  Eiver  Ship  and  Engine  Bldg.  Co.,  Quincy,  Mass. 

Glasgow  Iron  Works,  Pottstown,  Pa. 

C.  G.  Hussey  &  Co.,  Pittsburgh,  Pa. 

Midvale  Steel  Co.,  Wayne  Junction,  Pa. 

National  Tube  Co/s  Works  at 

Christy  Park,  Pa. 

McKeesport,  Pa. 

Elwood  City,  Pa. 

New  York  Shipbuilding  Co.,  Camden,  N.  J. 
Nicholson  File  Co.,  Providence,  R.  I. 
Niles-Benent-Pond  Co.,  Philadelphia,  Pa. 
and  branches 

Pond  Machine  Tool  Co.,  Plainfield,  N.  J. 

Pratt  &  Whitney  Co.,  Hartford,  Conn. 
Eeading  Steel  Castings  Co.,  Reading,  Pa. 
Schutte  and  Koerting  Co.,  Philadelphia,  Pa. 
Seneca  Iron  and  Steel  Co.,  Buffalo,  N.  Y. 
Worth  Bros.  Iron  Works,  Coatesville,  Pa. 
IT.  S.  Navy  Yard,  New  York,  N.  Y. 
U.  S.  Navy  Yard,  Boston,  Mass. 


PREFACE  5 

In  addition,  the  following  named  companies  have  contributed 
useful  information : 

Harbison  Walker  Eefractories  Co.,  Pittsburgh,  Pa. 

Illinois  Steel  Co.,  South  Chicago,  111. 

C.  W.  Leavitt  &  Co.,  New  York,  N.  Y. 

Manning,  Maxwell  and  Moore,  New  York,  N.  Y. 

Oliver  Machinery  Co.,  Grand  Eapids,  Mich. 

Eockwell  Furnace  Co.,  New  York,  N.  Y. 

United   Engineering  and  Foundry   Co.,   Pittsburgh,   Pa. 

The  manuscript  was  read  by  Captain  F.  W.  Bartlett,  IT.  S.  Navy, 
Head  of  the  Department  of  Marine  Engineering  and  Naval  Con- 
struction at  the  Naval  Academy,  and  many  valuable  suggestions  made 
by  him  are  embodied  in  the  text. 

G.  W.  DANFORTH,  U.  S.  Navy. 

U.  S.  NAVAL  ACADEMY,  September,  1911. 


TABLE  OF  CONTENTS 

CHAPTER  I. 

INTRODUCTORY.      ENGINEERING    MATERIALS. 

1.  Scope  of  Mechanical  Processes. — 2.  Study  of  Processes. — 3.  General 
Classification  of  Materials. — 4.  Materials  Most  Used. — 5.  Proper- 
ties of  Materials. — 6.  Influences  Which  Change  Properties  of 
Materials. — 7.  Fatigue  of  Metals. — 8.  Classification  of  Forces. — 
9.  Alloys. — 10.  Peculiarities  of  Alloys. — 11.  Designation  of  Weil- 
Known  Alloys. — 12.  Brass. — 13.  The  Bronzes. — 14.  Other  Useful 
Alloys. — 15.  Copper.  Its  Uses. — 16.  Properties  of  Copper. — 17. 
Uses  of  Zinc. — 18.  Properties  of  Zinc. — 19.  Uses  of  Tin. — 20. 
Properties  of  Tin. — 21.  Uses  of  Lead. — 22.  Properties  of  Lead. — 
23.  Uses  of  Nickel.— 24.  Properties  of  Nickel.— 25.  Uses  of 
Aluminum. — 26.  Properties  of  Aluminum. — 27.  Use  and  Proper- 
ties of  Antimony. — 28.  Portland  Cement  and  Concrete.  General 
Characteristics. — 29.  Varieties  of  Lime  and  Cement. — 30.  True 
Cements. — 31.  Requisites  in  Selecting  Raw  Materials, — 32.  Com- 
position of  Cement. — 33.  Manufacture  of  Portland  Cement. — 
34.  Uses  of  Portland  Cement. — 35.  Cement  Mixtures. — 36.  Method 
of  Using  Concrete. — 37.  Causes  of  Settling  and  Strengthening  of 
Cement. — 38.  Wood.  Use  as  Parts  of  Machinery. — 39.  Lumber 
and  Timbers. — 40.  Lumber  Grading. — 41.  Hard  and  Soft  Wood 
Lumber. — 42.  Heart  and  Sap  Wood. — 43.  Lumber  Inspection 
Rules. — 44.  Standard  Defects. — 45.  Rough  and  Dressed  Lumber. 
— 46.  Lumber  Measurement. — 47.  Durability  of  Wood 13 

CHAPTER  II. 

A  GENERAL  OUTLINE  OF  METAL-PRODUCING  PROCESSES. 
48.  Ores. — 49.  Elimination  of  Gangue. — 50.  Calcination. — 51.  Break- 
ing up  the  Ore  Compound. — 52.  Smelting  Furnaces. — 53.  The 
Blast  Furnace. — 54.  Blast  Furnace  Modifications. — 55.  Acid  and 
Basic  Ores. — 56.  Fluxes. — 57.  Blast  Furnace  Operation. — 58. 
The  Blast  Stove. — 59.  Reverberatory  Furnaces. — 60.  Atmosphere 
of  Reverberatory  Furnaces. — 61.  Refractory  Materials. — 62 
Sources  of  Copper. — 63.  Producing  Copper  from  its  Sulphides. — 
64.  The  Poling  Process.— 65.  Electrolytic  Refining  of  Copper. — 66. 
Zinc. — 67.  Tin. — 68.  Lead. — 69.  Nickel. — 70.  Aluminum. — 71. 
Electricity  in  Metallurgy 35 

CHAPTER  III. 

FUELS. 

72.  Uses. — 73.  Combustion. — 74.  Components  of  Fuels. — 75.  Classes 
of  Fuel. — 76.  Wood  and  Charcoal. — 77.  Coal. — 78.  Coke. — 79.  Coke 
Making.— 80.  Powdered  Coal. — 81.  Screenings.  Briquettes.— 82. 
Liq\iid  Fuels. — 83.  Gas  Fuels. — 84.  Natural  Gas. — 85.  Producer 
Gas.— 86.  Water  Gas.— 87.  Illuminating  Gas 58 


TABLE  OF  CONTENTS 


CHAPTER  IV. 

IRON  AND  STEEL. 

88.  Iron  Ores. — 89.  Preliminary  Preparation  of  Iron  Ores. — 90.  Cal- 
cination.— 91.  Reduction. — 92.  Pig  Iron. — 93.  Disposition  of  Iron 
from  the  Blast  Furnace. — 94.  Grades  of  Pig  Iron. — 95.  The 
Three  General  Classes. — 96.  Carbon  in  Iron. — 97.  Silicon  in  Iron. 
— 98.  Sulphur  in  Iron. — 99.  Phosphorus  in  Iron. — 100.  Manganese 
in  Iron. — 101.  Properties  of  Cast  Iron. — 102.  Properties  of 
Wrought  Iron. — 103.  Properties  of  Steel. — 104.  History  of 
Wrought  Iron. — 105.  Methods  of  Production. — 106.  The  Indirect 
Process  of  Wrought-Iron  Making. — 107.  The  Puddling  Furnace. 
—108.  Puddling-Furnace  Operation. — 109.  Treatment  of  Puddle 
Balls. — 110.  Re-heating  and  Welding  Muck  Bar  into  Wrougnt 
Iron. — 111.  Rolls  for  Shaping  Wrought  Iron. — 112.  History  of 
Steel.— 113.  The  Cementation  Process. — 114.  Present  Processes  of 
Steel  Making. — 115.  The  Bessemer  Process. — 116.  Operation  of 
the  Converter. — 117.  Pouring  the  Steel  into  Moulds. — 118. 
Features  of  the  Bessemer  Process. — 119.  The  Open-Hearth  Pro- 
cess.— 120.  The  Open-Hearth  Furnace. — 121.  Charging  the  Open- 
Hearth  Furnace. — 122.  Operation  of  the  Open-Hearth  Furnace. 
— 123.  Tapping  Out. — 124.  Pouring  the  Moulds. — 125.  The  Tal- 
bot  Process. — 126.  The  Duplex  Process. — 127.  Uses  of  Open- 
Hearth  Steel. — 128.  The  Crucible  Process. — 129.  Materials  used 
in  Crucible  Steel. — 130.  Crucibles. — 131.  The  Crucible  Furnace. 
— 132.  Charging  a  Crucible. — 133.  Operation  of  the  Crucible 
Furnace. — 134.  Properties  of  Crucible  Steel. — 135.  Special  Steels. 
— 136.  Ingot  Moulds.  Stripping  Ingots. — 137.  Impurities  in 
Steel.  Segregation. — 138.  Defects  in  Steel  Ingots. — 139.  Fluid 
Compressed  Steel. — 140.  Compressing  Steel. — 141.  The  Electric 
Refining  Furnace 68 

CHAPTER  V. 

MECHANICAL  TREATMENT  OF  METALS.— HEAT  TREATMENT 

OF  METALS. 

142.  Forms  of  Newly  Produced  Metals. — 143.  Primary  Outline  of 
the  Shaping  of  Metals. — 144.  Reducing  an  Ingot  to  Marketable 
Forms. — 145.  Re-heating  of  Ingots.  The  Soaking  Pit. — 146. 
Rolling  an  Ingot. — 147.  Mill  Scale. — 148.  Structural  Steel  Shapes. 
— 149.  Types  of  Rolling  Mills. — 150.  The  Cogging  Mill. — 151.  The 
Structural  Mill.— 152.  The  Billet  Mill.— 153.  The  Rail  Mill.— 
154.  The  Sheet-Bar  Mill.— 155.  Plate  Mills.— 156.  Names  of  Roll- 
ing-Mill  Parts. — 157.  Re-heating  of  Blooms,  Slabs  and  Billets. 
— 158.  Re-heating  Furnace  for  Large  Blooms. — 159.  Precautions 
in  Re-heating  High-Grade  Steel. — 160.  Points  for  the  Inspection 
of  Rolled  Material. — 161.  Effect  of  Mechanical  Treatment  of 
Metals.— 162.  Cold-Rolled  Steel.— 163.  Large  Forgings.— 164. 
The  Hydraulic  Forging  Press. — 165.  Handling  Large  Ingots  for 
Forging. — 166.  The  Heat  Treatment  of  Metals. — 167.  Changes  in 
Steel  Due  to  Heating.— 168.  Annealing  of  Metals.— 169.  The 
Hardening  of  Steel. — 170.  Oil  Tempering  of  Steel. — 171.  Rolling 
Sheet  Copper.  The  Sheet  Mill. — 172.  Rolling  of  Sheet  Brass. — 
173.  Extruded  Brass. — 174.  Extruded  Shapes 123 


TABLE  OF  CONTENTS  9 

CHAPTER  VI. 

THE  RE-MANUFACTURE  OF  METALS. 

175.  Scope  of  Metal  Re-Manufacturing. — 176.  Tool  Making. — 177. 
Special  Methods  of  Heating  and  Hardening  Steel  Articles. — 178. 
Sheet  Iron.— 179.  The  Manufacture  of  Sheet  Iron. — 180.  Galvan- 
izing.—181.  Tinning.— 182.  The  Manufacture  of  Tin  Plate  — 
183.  Terne  Plates. — 184.  Russia  Iron. — 185.  Wire  Drawing. — 186. 
Gaging  the  Sizes  of  Wire. — 187.  Coating  Wire  for  Protection 
from  Corrosion. — 188.  Hard  Wire.  Spring  Material. — 189.  Pipes 
and  Tubes.— 190.  The  Manufacture  of  Welded  Pipe.— 191.  Defects 
in  Welded  Pipe. — 192.  Iron  Pipe. — 193.  Seamless  Tubes. — 194. 
Piercing  Billets  for  Seamless  Tubes. — 195.  Rolling  Pierced 
Blanks. — 196.  Cross  Rolling. — 197.  Sizing. — 198.  Straightening 
and  Cutting  to  Length. — 199.  Cold-Drawn  Tubes. — 200.  Brass 
and  Copper  Tubing. — 201.  Tubes  of  Thin  Walls  and  Small  Di- 
ameters— 202.  Defects  in  Seamless  Tubes. — 203.  Hot-Drawn 
Seamless  Tubes. — 204.  Steel  Cylinders  for  Storage  of  Gases. — 
205.  Cold  Pressing  of  Metals. — 206.  Steps  in  Shaping  Articles  from 
Sheet  Metals. — 207.  Drop  Forgings. — 208.  The  Drop  Hammer. — 
209.  Drop-Forging  Dies.  Making  a  Drop  Forging. — 210.  Bolts, 
Nuts  and  Rivets.— 211.  Screw-Cutting  Machines. — 212.  Examples 
of  Work  from  the  Screw  Machine 158 


CHAPTER  VII. 

SHOPS  OF  MACHINERY  BUILDING  AND  REPAIRING  PLANTS.— 
DRAWINGS   FOR   SHOP   USE. 

213.  Distinctive  Features  of  Building  and  Repairing  Plants. — 214. 
Shops  Composing  a  Building  and  Repairing  Plant. — 215.  The 
Drawing  Room. — 216.  Drawing-Room  Methods. — 217.  Shop  Draw- 
ings.— 218.  Methods  of  Representing  Articles  on  Drawings. — 
219.  Consecutive  Order  of  Shop  Work 199 


CHAPTER  VIII. 

THE  PATTERN  SHOP. 

220.  Work  of  the  Pattern  Shop. — 221.  Pattern-Shop  Equipment. — 
222.  Power  Tools. — 223.  The  Circular  Saw. — 224.  The  Speed  Lathe. 
— 225.  Turning  Tools. — 226.  The  Wood  Lathe. — 227.  The  Face 
Lathe.— 228.  The  Band  Saw.— 229.  The  Hand  Planer.— 230. 
The  Surface  Planer. — 231.  The  Boring  Machine. — 232.  The  Mor- 
tise Machine. — 233.  Hand  Tools. — 234.  Materials  used  for  Pat- 
terns.—235.  Joints  and  Cuts  in  Woodworking. — 236.  Essential 
Features  of  Patterns. — 237.  Shrinkage  Allowance. — 238.  Draw- 
ing a  Pattern  from  the  Mould. — 239.  Core  Prints  and  Core  Boxes. 
— 240.  Fillets. — 241.  The  Prevention  of  Warping. — 242.  Marking 
and  Preserving  Patterns. — 243.  Pattern-Shop  Accessories  and 
Methods. — 244.  The  Laying-Down  Board. — 245.  The  Marking- 
Off  Table.— 246.  Varieties  of  Patterns. — 247.  Skeleton  Patterns. 
—248.  Sweeps 205 


10  TABLE  OF  CONTENTS 

CHAPTER  IX. 

THE   FOUNDRY. 

249.  The  Work  of  the  Foundry. — 250.  Iron,  Brass  and  Steel  Found- 
ries.— 251.  Classes  of  Moulds. — 252.  Example  of  an  Open  Sand 
Mould. — 253.  Example  of  a  Green  Sand  Mould. — 254.  Essential 
Features  of  a  Mould. — 255.  Foundry  Equipment. — 256.  Moulding 
Sand. — 257.  Other  Materials  Used  in  Moulding. — 258.  Flasks  for 
Green  and  Dry  Sand  Moulds. — 259.  Tools  Used  in  Moulding. — 
260.  Example  of  Making  a  Small  Mould. — 261.  Moulding  Ma- 
chines.— 262.  Cores. — 263.  Chaplets. — 264.  Chill  Moulds. — 265. 
Example  of  a  Loam  Mould. — 266.  Building  a  Loam  Mould. — 267. 
The  Cupola, — 268.  Operation  of  the  Cupola. — 269.  Ladles. — 270. 
Foundry  Iron. — 271.  Brass  Furnaces. — 272.  Defects  in  Castings. 
— 273.  Remedies  for  Defective  Castings.— 274.  Steel  Castings. 
— 275.  Steel  and  Iron  Foundries  Compared. — 276.  Moulds  for 
Steel  Castings. — 277.  Particular  Requirements  for  Steel  Moulds. 
— 278.  Surfaces  of  Steel  Moulds. — 279.  Means  of  Avoiding 
Shrinkage  Cracks. — 280.  Avoiding  Surface  or  Interior  Cavities. 
— 281.  Steel  for  Castings. — 282.  The  Tropenas  Converter. — 283. 
Temperature  of  Steel  for  Pouring. — 284.  Annealing  Steel  Cast- 
ings.— 285.  Defects  in  Steel  Castings 228 

CHAPTER  X. 

THE  BLACKSMITH  SHOP. 

286.  The  Blacksmith  and  Forge  Shop. — 287.  Materials  for  Forgings. 
— 288.  Shop  Equipment  for  Hand  Forging. — 289.  The  Forge. — 
290.  The  Anvil. — 291.  Smiths'  Hammers. — 292.  Tongs  and  Anvil 
Tools. — 293.  Fuel  for  Use  in  Forges. — 294.  Heating  in  a  Forge. 
— 295.  Terms  Commonly  Used  in  Forging. — 296.  Measuring  Stock 
for  Forging. — 297.  Welding. — 298.  Hardening  and  Tempering  at 
the  Forge. — 299.  Color  Table  for  Judging  Hardness. — 300.  Hard- 
ening of  Alloy-Steel  Tools. — 301.  Influence  of  the  Cooling  Me- 
dium in  Hardening. — 302.  Annealing  in  the  Blacksmith  Shop. 
— 303.  Equipment  of  the  Forge  Shop. — 304.  The  Steam  Hammer. 
305.  Appliances  Used  with  the  Steam  Hammer. — 306.  Heating 
Furnaces. — 307.  Notes  on  Steam  Hammer  Forging 260 

CHAPTER  XI. 

THE  MACHINE  SHOP. 

308.  Scope  of  Machine-Shop  Work. — 309.  Machine-Shop  Practice. — 
310.  Machine-Shop  Equipment. — 311.  Marking  Work  to  be  Ma- 
chined.—312.  The  Marking-Off  Table.— 313.  Tools  and  Appli- 
ances for  the  Marking-Off  Table. — 314.  Refined  Measuring  in 
Machine  Work. — 315.  Tools  for  Measuring. — 316.  The  Micrometer 
Caliper. — 317.  Machine  Tools. — 318.  The  Lathe. — 319.  Varieties  of 
the  Lathe. — 320.  Lathe  Tools. — 321.  Lathe  Attachments. — 322. 
The  Lathe  Chuck. — 323.  Lathe  Mandrels. — 324.  The  Boring  Bar. 
—325.  The  Steady  Rest. — 326.  Centering  Work  for  the  Lathe. 
— 327.  Cutting  of  Screw  Threads. — 328.  Forms  of  Threads.  Defi- 
nitions.— 329.  Standard  Threads. — 330.  Drilling  Machines. — 331. 
The  Vertical  Drill.— 332.  The  Radical  Drill.— 333.  Drills  and  At- 
tachments for  Drilling  Machines. — 334.  The  Planer. — 335.  Types 
of  the  Planer. — 336.  Planer  Tools. — 337.  The  Planer  Chuck  and 


TABLE  OF  CONTENTS  11 

Planer  Jack. — 338.  The  Planing  of  Propeller  Blades. — 339.  The 
Shaper. — 340.  The  Milling  Machine. — 341.  Description  of  the 
Milling  Machine. — 342.  The  Universal  Milling  Machine. — 343. 
Milling-Machine  Cutters  and  Arbors. — 344.  Milling-Machine  At- 
tachments.— 345.  The  Boring  Machine. — 346.  The  Horizontal 
Boring  and  Drilling  Machine. — 347.  The  Vertical  Boring  and 
Turning  Mill. — 348.  The  Slotting  Machine. — 349.  Tools  for  the 
Slotting  Machine. — 350.  Pipe  Cutting  and  Threading  Machines. 
—351.  Tool-Sharpening  Machines. — 352.  Metal-Cutting  Saws. — 
353.  Forcing  Presses. — 354.  Machine-Shop  Notes. — 355.  Bench 
Work  in  the  Machine  Shop.— 356.  Cold  Chisels.— 357.  Files.— 
358.  Taps  and  Dies. — 359.  Wrenches. — 360.  Scrapers. — 361.  Sur- 
face Plates. — 362.  Abrasive  Materials. — 363.  Portable  Tools. — 
364.  Pipe  Fitting. — 365.  Fittings. — 366.  Tools  Used  in  Pipe  Fit- 
ting.— 367.  Bolts,  Nuts  and  Machine  Screws 275 

CHAPTER  XII. 

THE  BOILER  SHOP. 

368.  Work  of  the  Boiler  Shop. — 369.  Types  of  Boilers.  Their  Man- 
ufacture.— 370.  Boiler  Material. — 371.  Preliminary  Diagram 
for  Laying  Out  Work. — 372.  Diagram  for  Laying  Out  Shell 
Plates. — 373.  Preparation  of  Plates  for  Laying  Out. — 374.  Opera- 
tions for  Shaping  Plates. — 375.  Planing  Plate  Edges. — 376. 
Plate-Bending  Rolls. — 377.  Marking  a  Flange. — 378.  Methods 
of  Flanging. — 379.  Equipment  for  Flanging  by  Hand. — 380.  The 
Hydraulic  Flanging  Press. — 381.  The  Hydraulic  Accumulator. 
— 382.  Flange-Heating  Furnace. — 383.  Straightening  and  An- 
nealing of  Flanged  Plates. — 384.  Drilling  Holes  in  Boiler  Plates. 
—385.  Assembling  the  Parts  of  a  Boiler.— 386.  Riveting.— 387. 
Rivet-Heating  Furnace. — 388.  Methods  of  Holding  Boiler  Tubes 
in  Place. — 389.  Chipping  and  Caulking. — 390.  Corrugated  Fur- 
naces.— 391.  Other  Equipment  for  the  Boiler  Shop. — 392.  Power 
Shears  and  Punch. — 393.  Hand  Shears  and  Punch. — 394.  Shapes 
of  Rivets 338 

CHAPTER  XIII. 

OTHER  SHOPS— SPECIAL  PROCESSES. 

395.  Sheet  Metal  Work. — 396.  The  Copper  Shop.  Materials  Used. 
— 397.  Copper  Shop  Equipment. — 398.  Cutting,  Bending  and 
Riveting  Tools. — 399.  Coppersmith  Hammers. — 400.  Brazing. — 
401.  Heat  for  Brazing. — 402.  Annealing. — 403.  Soldering. — 404. 
Method  of  Soldering. — 405.  Copper  Pipe. — 406.  Joining  Lengths 
of  Copper  Pipe. — 407.  Brazing  a  Branch  in  a  Copper  Pipe. — 
408.  The  Plate  and  Angle  Shop. — 409.  The  Bending  Slab. — 410. 
Special  Processes. — 411.  Malleableizing. — 412.  Case  Hardening. 
— 413.  Pipe  Bending. — 414.  Joining  Metals. — 415.  Electric  Weld- 
ing.— 416.  The  Resistance  System. — 417.  The  Arc  System. — 418. 
The  Thermit  Process. — 419.  Making  a  Thermit  Weld. — 420.  Blow 
Pipe  Welding.— 421.  Method  of  Making  a  Blow  Pipe  Weld.— 422. 
Application  of  Blow  Pipe  Welding. — 423.  Blow  Pipe  Cutting  of 
Metals. — 424.  Burning  On. — 425.  Puddling. — 426.  Classification 
of  Welding.  Methods. — 427.  Grinding. — 428.  Grinding  Machines. 
— 429.  Grinding  Wheels. — 430.  Lapping. — 431.  Armor-Plate 
Making  363 


12  TABLE  OF  CONTENTS 

APPENDIX. 

432.  Table  of  Brasses  and  Bronzes. — 433.  Degrees  of  Hardness  of 
Steel  Tools. — 434.  File  Making. — 435.  Wire  Gage  Table. — 436 
Wire  Dies.— 437.  Dimensions  of  Standard  Iron  Pipes.— 438! 
Methods  of  Threading  Bolts. — 439.  Illustration  of  Automatic 
Screw  Machine  Work. — 440.  Shop  Location  and  Equipment. — 
441.  Allowance  for  Forcing  and  Shrinkage  Fits. — 442.  U.  S. 
Standard  Screw  Threads. — 443.  Hydraulic  Data 395 

INDEX .  407 


CHAPTEE  I. 
INTRODUCTORY.     ENGINEERING  MATERIALS. 

1.  Scope  of  Mechanical  Processes. — Mechanical  processes  prop- 
erly include  every  manual  and  machine  process,  and  the  mechanical 
part  of  every  chemical  process,  used  in  the  extensive  field  of  the 
mechanical  arts.    This  broad  field  includes  every  branch  of  manu- 
facturing and  construction.     It  would  be  obviously  impracticable 
to  attempt  to  cover  this  field  in  one  book,  hence  it  is  intended  to 
include  here  a  brief  account  of  (1)  the  more  important  materials 
of  construction  and  the  essential  steps  in  producing  them;  and  (2) 
the  methods  of  shaping  metals  for  use,  particularly  the  shop  proc- 
esses much  used  in  mechanical  and  marine  engineering  construction. 

To  give  a  full  account  of  all  that  investigators  have  brought  to 
light  of  the  properties  of  the  commonly  used  engineering  materials, 
and  of  all  the  methods  devised  for  shaping  them  into  useful  forms, 
would  require  the  space  of  many  volumes,  and  then  the  subject 
would  not  be  exhausted,  as  doubtless  many  facts  and  methods  are 
yet  undeveloped.  Attempt  is  made  herein  to  give  the  student  an 
elementary  understanding  of  the  materials  and  methods  employed 
in  machine  building,  for  use  of  those  who  enter  or  must  come  into 
intelligent  contact  with  modern  engineering. 

2.  Study  of  Processes. — Every  process  involves  time,  labor,  and 
expense,  and  is  employed  in  whole  or  in  part  only  because  it  accom- 
plishes a  definite  and  necessary  purpose.     Its  use  must  be  justified 
as  a  necessary  step  toward  a  definite  result,  else  there  would  be  no 
reason  for  employing  it.    A  process  may  not  be  perfect,  although  it 
may  bring  excellent  results,  and  improvements  in  processes   are 
being  made  constantly,  despite  the  remarkable  degree  of  skill  at 
present  existing  in  the  production  and  shaping  of  metals  for  a  great 
variety  of  uses. 

From  a  superficial  knowledge  of  the  properties  of  metals,  many 
remarkable  processes  of  shaping  them  hot  or  cold  have  been  gradu- 


14  MECHANICAL  PROCESSES 

ally  evolved  or  improved  upon  by  patient  and  persistent  experi- 
ments, and  methods  for  shaping  metals  are  now  in  vogue  which 
were  deemed  impossible  a  decade  ago.  Success  along  these  lines 
comes  only  from  testing  the  properties  of  a  material  beyond  the 
known  range,  studying  the  causes  of  failure,  and  bringing  to  one's 
aid  improved  apparatus  for  holding,  pressing,  cutting,  heating,  etc., 
as  necessity  may  require. 

The  details  of  many  processes  vary  because  of  difference  in  the 
skill  of  workmen,  or  difference  in  equipment  or  quality  of  materials 
with  which  they  work. 

3.  General  Classification  of  Materials. — The  materials  used  in  all 
branches  of  construction  are  commonly  called  engineering  materials 
or  materials  of  construction.    The  most  important  of  these,  as  iron, 
steel,  brass,  wood,  stone,  etc.,  are  well  known.     There  are  many 
other  materials  less  extensively  used,  and  more  or  less  widely  known. 

Another  class  of  materials  necessary  to  the  various  processes  in- 
clude those  employed  to  assist  the  processes,  though  not  intended 
to  enter  into  the  finished  product,  as  fuel,  flux  in  smelting  and  in 
welding,  emery  in  grinding,  sand  in  moulding,  etc. 

4.  Materials  Most  Used. — The  material  most  extensively  used  in 
engineering  construction  is  iron  in  its  several  forms,  included  under 
three  divisions,  viz.,  wrought  iron,  steel  and  cast  iron.   The  materials 
of  these   three   divisions   are  made  the  subjects  of  a  subsequent 
chapter.    Other  materials,  of  varying  degrees  of  importance,  are: 

Alloys,  Nickel, 

Copper,  Aluminum, 

Zinc,  Antimony, 

Tin,  Portland  cement. 

Lead,  Wood. 

5.  Properties  of  Materials. — All  materials  have  certain  physical 
properties  which  determine  their  fitness  for  specific  purposes.     Of 
first   consideration    in   materials    of    construction   is    strength,    or 
tenacity,  which  is  the  attraction  between  molecules  of  a  material 
giving  them  the  power  to  resist  tearing  apart.     Next  in  considera- 
tion is  the  property  of  a  material  which  allows  a  change  of  relative 
position  of  its  molecules  (which  is  change  of  shape),  without  de- 
stroying or  seriously  affecting  tenacity. 


INTRODUCTORY.     ENGINEERING  MATERIALS  15 

Specific  properties  of  materials  are : 

(1)  Hardness,  the  property  of  resisting  change  of  shape  tinder 
pressure  and  separation  into  parts. 

(2)  Brittleness,  associated  with  hardness,,  the  property  of  resist- 
ing a  change  of  the  relative  position  of  molecules,  or  liability  to 
fracture  without  change  of  shape. 

(3)  Density,  the  weight  of  a  unit  volume  usually  compared  with 
unit  volume  of  water. 

(4)  Elasticity,   the   power   of   returning  to   the   original   shape 
upon  removal  of  the  force  which  has  caused  change  of  shape. 

(5)  Ductility,  the  property  of  metals  allowing  them  to  be  drawn 
out,  as  in  wire-making,  without  breaking. 

(6)  Malleability,   similar  to   ductility,   the   property   of   metals 
allowing  them  to  bend  or  be  permanently  distorted  without  rupture. 
Examples  of  this  are  rolling  a  metal  into  sheets  or  changing  its 
form  by  hammering.    Opposed  to  brittleness. 

(7)  Fusibility,  the  property  of  being  liquefied  by  heat. 

(8)  Conductivity,   the  power  to   transmit  molecular  vibrations 
caused  by  heat  or  electricity. 

(9)  Contraction  and  expansion,  the  change  of  volume  due  to 
change  of  temperature. 

6.  Influences  Which  Change  Properties  of  Materials. — Heat  has 
more  or  less  influence  in  changing  these  properties  in  a  given  ma- 
terial. 

Hardness  and  strength  are  increased  by  hammering  or  rolling  a 
metal,  and  these  properties  are  changed,  often  in  a  marked  degree, 
by  a  slight  amount  of  another  substance  in  the  metal. 

Conductivity  is  usually  increased  or  decreased  by  heat,  and  elec- 
tric conductivity  is  greatly  reduced  by  impurity  in  metals. 

Some  metals  and  alloys  expand  upon  cooling,  due  to  certain 
ingredients. 

Heating  and  cooling  suddenly,  will  render  steel  hard  and  brittle, 
and  annealing.,  which  is  a  different  process  for  different  metals, 
brings  a  metal  or  an  alloy  back  to  its  natural  or  normal  state  of 
softness  after  having  been  hardened  by  hammering,  rolling,  or 
otherwise. 

7.  Fatigue  of  Metals. — It  has  been  found  that  metals  give  way  in 
some  cases  under  smaller  loads  than  they  could  originally  carry. 


16  MECHANICAL  PROCESSES 

This  is  called  fatigue,  and  is  caused  by  a  very  great  number  of 
reversals  or  repetitions  of  load,  as  when  a  metal  receives  constant 
shocks  or  impacts  in  use.  It  is  a  popular  but  erroneous  idea  that 
the  particles  of  metal  change  to  a  weakened  crystalline  form. 
Later  investigations  show  that  the  loss  of  strength  is  due  to  the 
crystals  of  metal  being  so  shaken  that  the  small  planes  of.  cleavage 
between  them  join  in  one  continuous  plane  of  rupture,  which,  when 
sufficiently  extended,  leaves  the  remaining  sound  metal  unable  to 
resist  the  shock  brought  upon  it.  Cases  of  fatigue  are  unusual. 

8.  Classification  of  Forces. — Forces  acting  upon  materials  are 
classified  according  to  their  direction  of  action. 

A  force  acting  on  a  material  is  called  a  stress,  and  the  deforma- 
tion caused  by  this  action  is  the  consequent  strain. 

If,  upon  removal  of  the  force,  the  material  returns  to  its  original 
shape,  the  strain  has  been  within  the  elastic  limit  of  the  material, 


FIG.  1. 

but  if  upon  removing  the  force,  the  material  fails  to  resume  its 
original  shape,  it  has  been  strained  beyond  its  elastic  limit,  and  is 
said  to  have  a  permanent  set.  If  the  force  continues  to  be  increased 
beyond  that  causing  permanent  set,  a  rupture  of  the  material  will 
finally  result. 

Tension  is  the  action  of  forces  tending  to  pull  apart  the  particles 
of  a  material,  and  tensile  strength  of  a  material,  expressed  in 
pounds  per  square  inch  of  cross  section  of  the  material  pulled,  is  a 
measure  of  the  force  required  to  disrupt  the  material.  The  amount 
which  a  metal  stretches  in  pulling  apart  is  called  the  elongation. 
This  is  expressed  as  a  per  cent  of  the  original  length  of  the  metal 
specimen  subjected  to  tension. 

Compression  is  the  crushing  action  of  forces. 

Torsion  is  the  twisting  action  of  forces. 

Shearing  is  the  action  of  forces  tending  to  cause  adjacent  parts 
of  a  material  to  move  in  opposite  directions  parallel  to  a  plane  of 
cleavage. 


INTRODUCTORY.     ENGINEERING  MATERIALS  17 

To  illustrate  the  result  of  bending,  consider  that  a  piece  of  ma- 
terial is  bent  as  shown  in  Fig.  1.  Its  fibres  or  particles  along  AB, 
and  for  a  distance  thereunder,  are  in  tension  and  are  slightly  elon- 
gated, while  fibres  or  particles  along  FGr,  and  for  a  distance  above, 
are  in  compression,  and  are  slightly  shortened. 

There  is  a  portion  of  the  piece  along  CD  which  is  neither  under 
tension  nor  compression  and  remains  of  unchanged  length.  This  is 
called  the  neutral  axis. 

9.  Alloys. — An  alloy  is  a  combination  formed  by  stirring  together 
two  or  more  metals  (occasionally  with  other  substances  introduced) 
in  a  state  of  fusion.    Investigators  state  that  some  alloys  are  chem- 
ical combinations,  some  are  mechanical  mixtures  and  others  are 
apparently  solutions  of  one  metal  in  another. 

10.  Peculiarities  of  Alloys. — Alloys  have  peculiarities  demanding 
special  and  extensive  study  to  understand  them,  and  no  laws  have 
yet  been  found  by  which  the  properties  of  an  alloy  may  be  deter- 
mined from  the  properties  of  its  constituents.     The  properties  of 
an  alloy  are  not  an  average  of  like  properties  in  its  constituents, 
and  very  unexpected  results  may  be  obtained  by  varying  the  propor- 
tions of  constituents  of  an  alloy,  or  by  introducing  the  slightest 
amount  of  some  other  ingredient. 

The  following  items  give  the  important  peculiarities  of  alloys: 

(1)  The  strength  of  some  alloys,  particularly  when  hammered, 
rolled  or  drawn  into  wire,  is  much  greater  than  that  of  any  of  the 
composing  metals.    This  is  true  of  the  useful  brasses  and  bronzes. 

(2)  Varying  the  proportions  of  the  same  metals  in  an  alloy 
throughout   a   wide   range   will   give  very   different   products    in 
strength,  hardness,  malleability,  ductility,  density,  fusion  point,  and 
color.    These  changes  will  not  come  in  a  line  of  regularity.     Some 
of  the  products  will  differ  widely  from  the  rest. 

(3)  The  fusing  point  of  an  alloy  is  usually  lower  than  the  aver- 
age of  the  fusing  points  of  the  constituents,  and  sometimes  lower 
than  the  fusing  point  of  any  constituent.     Some  alloys,  composed 
of  about  50%  of  bismuth,  melt  below  the  temperature  of  boiling 
water. 

(4)  The  introduction  of  a  slight  amount  of  some  metals,  metal- 
loids or  impurities  in  a  given  alloy  may  bring  great  changes  to  one 


18  MECHANICAL  PROCESSES 

or  more  of  its  properties,  sometimes  improving  the  alloy,  but  more 
frequently  rendering  it  worthless. 

(5)  The  order  of  melting  and  mixing  the  several  metals  of  an 
alloy  influences  the  quality  of  the  alloy,  because  some  metals  oxidize 
more  readily  than  others  in  the  fused  state.  This  oxidation  should 
be  reduced  to  a  minimum  because  it  wastes  the  metal  and  the  oxide 
weakens  the  alloy. 

In  making  alloys,  it  is  needless  to  attempt  to  get  good  results  by 
using  any  but  the  purest  of  commercial  metals,  and  scrap  alloys 
may  be  used  only  when  their  composition  is  known  and  when  it  i& 
suitable  to  the  correct  proportioning  of  the  mixture  to  be  made. 

The  principal  requirements  in  melting  metals  for  alloys  are 
(1)  melt  the  metal  of  highest  fusion  point,  and,  when  melted,  drop 
in  the  other  metal  broken  up  in  chunks;  (2)  have  the  molten  sur- 
face of  metal  covered  with  salt  or  other  flux,  or  with  charcoal,  to 
prevent  oxidation  from  atmospheric  oxygen;  (3)  stir  the  metals 
well  with  an  iron  rod  before  pouring  from  the  crucible. 

If  the  metals  in  an  alloy  are  not  thoroughly  mixed,  they  may  not 
form  a  homogeneous  mass  upon  cooling.  The  separating  out  of  any 
masses  of  one  of  the  metals  is  called  liquation.  This  condition  will 
not  likely  show  on  the  surface  of  the  alloy  when  cold,  but  will  affect 
strength  and  other  qualities. 

11.  Designations  of  Weil-Known  Alloys. — The  most  extensively 
used  of  all  alloys  are  those  consisting  mainly  of  copper.     Their 
ornamental  appearance  and  non-corrosive  quality  make  them  de- 
sirable, and  their  strength,  with  varying  degrees  of  hardness,  elas- 
ticity,   ductility    and   malleability,    supplies    the   requirements    for 
materials  of  a  wide  range  of  use. 

In  general,  copper-zinc  alloys  are  called  brass,  although  some 
brass  may  contain  also  a  small  amount  of  lead  or  tin;  copper-tin 
alloys  are  the  main  constituents  of  bronze;  and  copper-tin-zinc 
alloys  are  known  as  composition.  These  terms,  as  will  be  learned, 
are  loosely  used  in  practice  and  not  confined  to  the  designations 
here  given. 

12.  Brass. — This   is  one  of  the  most   important  of  the   alloys. 
While  its  usual  constituents,  copper  and  zinc,  combine  in  any  pro- 
portion, the  range  of  useful  proportions  varies  from  about  60  to 


INTRODUCTORY.     ENGINEERING  MATERIALS  19 

89%  of  copper.  A  widely  used  formula  for  brass  is  about  %  cop- 
per and  1/3  zinc. 

The  range  of  composition  of  brass  offers  a  material  suitable  for 
a  great  number  of  particular  uses.  Zinc  gives  brass  its  hardness, 
and  tin  in  small  quantities  increases  this.  Experiment  shows  that 
the  tensile  strength  of  cast  brass  is  greatest  (about  50,000  Ibs.  per 
sq.  in.)  when  the  composition  is  about  62%  copper  and  38%  zinc; 
and  that  ductility  and  malleability  are  greatest  for  about  70% 
copper  and  30%  zinc.  These  properties,  however,  are  improved  by 
adding  a  small  amount  of  tin  for  hardness,  or  lead  for  ductility. 

Brass  may  be  considerably  hardened  by  rolling  or  hammering, 
hot  or  cold,  or  by  drawing  it  into  wire.  Its  strength  and  rigidity 
are  by  these  means  increased,  and  brass  thus  treated  is  used  for 
springs,  but  these  effects  may  be  removed  by  annealing,  which  con- 
sists of  heating  to  a  cherry-red  and  cooling  slowly,  or  rapidly,  if  its 
composition  will  not  cause  cracking.  Thoroughly  annealed  brass 
has  no  springiness  and  may  be  bent  like  lead. 

13.  The  Bronzes. — Phosphor,  manganese  and  aluminum  bronzes 
are  among  the  best  bronzes  known,  and  are  the  most  extensively  used. 
Bronzes  are  used  when  a  strong  and  fairly  ductile  non-corrosive  alloy 
is  necessary  in  ship  and  machinery  parts.  They  are  the  strongest 
and  about  the  most  expensive  alloys  in  engineering  use.  Phosphorus 
and  manganese  are  used  in  the  bronzes  designated  by  these  names 
merely  to  assist  in  purging  the  molten  mixtures  of  metallic  oxides, 
thus  producing  alloys  of  greater  metallic  purity  and  consequently 
of  greater  strength. 

Aluminum  and  copper  seem  to  form  a  chemical  union  of  remark- 
able strength  and  ductility,  having  properties  resembling  those  of 
mild  steel.  The  alloy  can  be  forged  at  a  red  heat,  it  makes  excellent 
castings,  its  strength  is  greatly  increased  by  hammering  or  rolling, 
and  it  resists  the  corrosive  action  of  air  and  salt  water. 

Generally,  the  bronzes  can  be  considerably  strengthened  by  ham- 
mering or  rolling,  can  be  forged  hot,  (but  not  welded  in  a  black- 
smith forge),  and  their  hardness  increases  as  the  per  cent  of  copper 
is  lessened,  while  ductility  increases  as  the  copper  is  increased.  The 
less  ductile  mixtures  should  be  rolled  or  worked  hot.  A  peculiarity 
of  the  copper-tin  alloys  is  that  quick  cooling  in  water  tends  to  re- 


20  MECHANICAL  PROCESSES 

move  brittleness  and  to  increase  ductility  and  softness,  while  slow 
cooling  from  a  red  heat  restores  the  original  hardness. 

The  bronzes  are  less  ductile  than  brass,  and  those  to  be  rolled 
into  sheets  or  drawn  into  wire  must  not  contain  as  much  tin  as 
those  to  be  cast.  Their  hardness  makes  them  excellent  for  ma- 
chinery bearings.  Propellers  and  many  ship  fittings  are  made  of 
bronze  because  of  its  strength  and  resistance  to  salt  water  corrosion. 

14.  Other  Useful  Alloys  in  engineering  work  are : 
Anti-Friction  Metal,  used  to  line  bearings  for  shafts;  composed 

of 

Best  refined  copper 3.7  per  cent 

Banca  tin   88.8     "      " 

Eegulus  of  antimony 7.5     "      " 

These  must  be  well  fluxed  with  borax  and  rosin  in  mixing. 
Monel  Metal,  for  blades  of  steam  turbines. 
Nickel,  not  less  than  60  per  cent; 
Copper,  remainder  to  make  up  100  per  cent. 
A  monel  metal  consisting  of  nickel,  copper,  and  iron  is  refined 
from  a  deposit  of  natural  alloy  of  these  metals.    It  is  much  cheaper 
than  the  made-up  alloy  and  is  well  adapted  to  practical  use,  al- 
though its  proportions  are  not  likely  to  be  always  the  same. 
Another  alloy  recently  brought  into  use  consists  of 

Aluminum  90  per  cent 

Magnesium    10     "       " 

This  alloy  is  lighter  and  stronger  than  aluminum,  and  will 
doubtless  find  extensive  use  in  airship  construction,  and  possibly 
for  castings  for  submarine  and  other  naval  uses,  where  lightness 
and  strength  are  requisite  features. 

15.  Copper.    Its  Uses. — Copper  is  next  in  importance  to  iron  aa 
a  metal  of  the  useful  arts,  though  it  is  used  mostly  in  alloys.     Its 
principal  uses  are: 

(1)  As  the  main  constituent  of  most  of  the  useful  alloys. 

(2)  For  pipes  and  tubes  to  convey  steam  and  liquids.    A  coating 
of  tin  is  frequently  given  copper  pipes  and  tubes  used  to  convey 
liquids  to  aid  in  resisting  corrosion. 


INTRODUCTORY.     ENGINEERING  MATERIALS  21 

(3)  As  wire  for  resisting  corrosion  and  particularly  for  electric 
conductors  because  of  its  high  degree  of  conductivity  when  pure. 

(4)  For  sheathing  and  fastenings  of  wooden  ships. 

16.  Properties  of  Copper. — The  color  of  copper  is  dull  red.    In 
malleability  and  ductility,  either  hot  or  cold,  it  ranks  very  high. 
Its  tensile  strength  is  about  30,000  Ibs.,  although  rolling,  ham- 
mering or  drawing  it  into  wire  nearly  doubles  its  strength.    It  fuses 
at  about  1985°   F.     The  most  striking  properties  of  copper  are, 
(1)    the  adverse  way  in  which  the  smallest  amount  of  impurity 
affects  it,  and  (2)  its  superior  conductivity  for  heat  and  electricity 
when  pure  (99.9%). 

It  is  easily  forged  or  rolled  hot  or  cold  and  when  worked  cold  it 
becomes  hard,  as  in  wire  drawing,  but  it  may  be  again  softened,  or 
annealed,  by  heating  to  red  heat  and  plunging  into  cold  water, 
which  also  causes  a  loss  of  the  tensile  strength  gained  by  working. 

Commercial  copper  is  often  very  impure,  containing  arsenic, 
antimony,  copper  oxide,  iron,  and  lead,  according  to  the  ores  from 
which  extracted.  This  must  be  refined,  and  should  then  be  99.8% 
pure  for  high  grade  uses.  Refineries  supply  copper  for  market  in 
(1)  "pigs"  for  melting  and  making  alloys,  (2)  slabs  for  rolling 
into  sheets  for  various  uses,  and  (3)  ingots  for  wire  or  tube- 
drawing. 

17.  Uses  of  Zinc. — The  principal  uses  for  this  metal  are  as  fol- 
lows: 

(1)  The  most  important  use  is  for  alloying  with  copper  in  mak- 
ing brass  or  composition. 

(2)  When  zinc  is  exposed  to  air  or  water,  a  durable  and  im- 
permeable coating  of  zinc  carbonate  is  formed  on  the  surface  of  the 
metal.    This  makes  it  useful  for  galvanizing  iron  to  protect  against 
rusting.    Zinc  sheets  may  be  used  for  sheathing  or  roofing. 

(3)  Zinc   is  the  most  electro-positive   of  the  common  metals. 
This  makes  it  particularly  useful  as  a  protection  against  galvanic 
corrosion  in  steam  boilers,  and  on  the  hulls  of  steel  ships.     Copper, 
brass  and  bronze  may  also  be  protected  by  its  use.    Rolled  zinc  slabs 
are  bolted  in  scraped  metallic  contact  with  the  part  to  be  protected, 
and  the  electrolytic  action  of  impure  water  in  which  the  metals  are 
immersed  gradually  corrodes  the  zinc,  leaving  the  protected  metal 
intact.     However,  when  the  zinc  becomes  much  corroded  and  its 


22  MECHANICAL  PROCESSES 

metallic  surface  is  no  longer  exposed,  the  zinc  compound  resulting 
from  the  corrosion  acts  electro-negative  to  the  protected  metal  and 
this  metal  is  itself  destroyed.  The  protection  of  iron  by  galvaniz- 
ing, as  mentioned  in  item  (2),  is  due  not  only  to  a  coating  of  zino 
but  to  the  fact  that  when  a  part  of  the  zinc  coating  is  broken  and 
the  iron  is  exposed,  dampness  sets  up  an  electric  current  which  con- 
sumes the  zinc  instead  of  the  iron. 

(4)  Zinc  plates  are  used  extensively  in  electric  batteries. 

(5)  Oxide  and  sulphide  of  zinc  are  used  to  make  a  superior  grade 
of  white  paint. 

18.  Properties  of  Zinc. — Zine  has  a  bluish-white  color.   Its  malle- 
ability and  ductility  are  confined  to  certain  narrow  limits  of  tem- 
perature, and  it  must  be  maintained  at  a   temperature  of  about 
240°   F.  when  it  is  being  rolled  into  sheets.     It  melts  at  about 
800°  F.,  and  boils  at  about  1900°  F.     It  is  hard,  brittle  and  highly 
crystalline  in  fracture,  and  if  the  fracture  shows  dull  specks,  an 
excess  of  iron  is  present.     Boiled  zinc  is  more  dense  than  the  cast 
metal,  and  can  be  bent  to  a  moderate  degree. 

Commercial  zinc  is  known  as  spelter,  and  its  impurities  are 
mostly  lead  and  iron. 

19.  Uses  of  Tin. —  (1)   The  most  important  engineering  use  of 
this  metal  is  in  alloys. 

(2)  It  is  used  extensively  for  coating  sheets  of  iron  to  prevent 
corrosion,  and  these  sheets  are  widely  known  as  "  tin  " ;  also  it  is 
used  to  coat  copper,  brass  and  iron  wire,  pipes,  and  tubes,  by  dipping 
them  into  melted  tin. 

(3)  It  is  used  as  an  ingredient  of  solder  and  brazing  metal. 

20.  Properties  of  Tin. — Tin  has  nearly  the  whiteness  of  silver. 
It  is  very  malleable  and  flexible,  but  not  elastic.    Its  tensile  strength 
is  too  low  for  it  to  be  drawn  into  wire.     Air  will  not  tarnish  it 
readily,   but   some   acids   and   strong   alkaline    solutions    attack   it 
noticeably,  particularly  when  hot, 

It  is  a  poor  conductor  of  heat  and  electricity.  When  pure,  a  bar 
or  sheet  of  tin  makes  a  crackling  sound  when  bent,  called  the  "  cry 
of  tin,"  and  as  this  sound  is  destroyed  by  lead  as  an  impurity,  this 
fact  is  often  made  use  of  in  testing  tin.  It  melts  at  about  445°  F. 

Tin  is  marketed  in  small  ingots,  and  is  known  as  ''  Straits," 
"Banca,"  "Malacca,"  "Australian,"  etc.,  according  to  its  source. 


INTRODUCTORY.       ENGINEERING    MATERIALS  23 

Its  usual  impurities  are  lead,  iron,  copper,  and  antimony.     Good 
tin  should  be  99.75%  pure. 

21.  TJses  of  Lead. — This  metal  has  several  minor  uses  in  engi- 
neering. Of  these  the  principal  uses  are : 

( 1 )  As  sheet  lead  for  lining  tanks  and  basins  because  of  its  power 
to  resist  corrosion  from  air  and  from  many  dilute  acids. 

(2)  As  pipes  in  plumbing  work  due  to  its  flexibility,  ease  of 
soldering,  and  qualities  mentioned  in  item  (1),  although  it  cannot 
stand  high  heat  or  high  pressure. 

(3)  As  wire  for  gaging  tightness  of  large  engine  bearings,  and 
for  electric  fuses. 

(4)  As  pigments  for  well-known  paints  in  the  form  of  "  red 
lead"  (oxide  of  lead),  and  of  "white  lead"  (lead  carbonate). 

(5)  Occasionally   for   alloying   in   small   quantities   with   other 
metals  to  increase  ductility  and  malleability. 

22  Properties  of  Lead. — Lead  has  a  blue-gray  color.  It  is  the 
softest  and  heaviest  of  the  common  metals.  It  is  very  malleable 
and  ductile,  but  has  no  elastic  strength,  and  its  tensile  strength  is 
so  low  that  it  cannot  be  drawn  readily  into  fine  wires.  It  is  a 
poor  conductor  of  heat  and  electricity.  On  account  of  its  softness 
it  can  be  readily  squeezed  through  a  press  and  thus  shaped  into 
rods  or  pipes.  It  melts  at  about  600°  F. 

The  best  grade  of  commercial  lead  should  be  99.5%  pure. 

23.  Uses  of  Nickel. —  (1)   A  very  important  engineering  use  for 
this  metal  is  in  alloy  with  steel.    Its  addition  to  mild  steel  gives  a 
product  of  great  elastic  and  tensile  strength  and  fair  ductility.     Its 
presence  in  steel  lessens  corrosion. 

(2)  Another  alloy  of  nickel  of  importance  is  monel  metal. 

(3)  The  use  of  nickel  for  plating  metal  articles  is  well  known. 

(4)  In  commercial  alloys,  principally  German  silver,  nickel  is 
extensively  used;  also  an  alloyed  nickel  is  used  for  small  coins. 

24.  Properties  of  Nickel. — Xickel  is  white  with  a  bluish  tinge. 
It  is  malleable  and  ductile      It  has  about  the  same  hardness  and 
fusion  point  as  iron,  and  is  heavier  than  iron,  to  which  it  is  closely 
related,  having  magnetic  properties. 

25.  TJses  of  Aluminum. — The  principal  uses  of  aluminum  are  in 
making  aluminum  bronze,  and  as  pressed  sheet  or  cast  aluminum 


24  MECHANICAL  PROCESSES 

for  various  utensils  and  fittings  where  extreme  lightness  and  fair 
strength  are  required. 

26.  Properties  of  Aluminum. — This  metal  presents  a  remarkable 
combination  of  qualities.     It  is  the  lightest  of  the  useful  metals 
(excepting  magnesium.,  which  has  only  limited  uses  as  a  metal), 
has  many  exceptional  uses,  is  more  abundant  in  nature  than  any 
other  known  metal,  and  is  extracted  by  a  process  quite  apart  from 
general  metal  extraction  methods. 

Its  physical  qualities  are  as  follows : 

Color,  silvery  white. 

Malleability  and  ductility,  slightly  less  than  that  of  copper. 

Tensile  strength,  varying  from  about  16,000  Ibs.  for  cast  metal 
to  about  25,000  Ibs.  for  rolled  metal.  Annealing  slightly  decreases 
the  strength  of  rolled  metal. 

Fusing  point,  about  1200°  F. 

Specific  gravity,  about  2.6,  or  about  %  the  weight  of  iron. 

It  is  an  excellent  conductor  of  heat  and  electricity,  does  not  cor- 
rode in  air  or  in  water  to  a  noticeable  degree,  but  it  can  be  soldered 
only  with  much  difficulty  due  to  the  fact  that  the  pure  metallic  sur- 
face quickly  unites  with  oxygen,  forming  a  film  on  which  the  solder 
will  not  hold. 

Aluminum  is  not  so  soft  as  copper,  and  when  hammered  assumes 
the  hardness  of  hard  brass,  although  annealing  (heating  to  a  red 
heat  and  cooling  slowly)  again  renders  it  pliable. 

In  melting  it  for  castings,  an  ordinary  crucible  should  be  used, 
but  flux  should  not  be  used  because  of  the  chemical  combination 
likely  to  result.  It  shrinks  much  on  cooling. 

27.  Use  and  Properties  of  Antimony. — In  engineering  uses  this 
metal  serves  as  a  hardening  constituent  for  anti-friction  alloys.    It 
also  causes  these  alloys  to  expand  after  they  are  poured  into  place, 
making  them  fill  completely,  when  cold,  the  space  intended   for 
them.     It  is  grayish  white,  extremely  brittle,  has  a  peculiar  odor, 
and  melts  at  about  850°  F. 

Its  usual  commercial  form,  the  regulus  of  antimony,  is  a  some- 
what impure  metal  extracted  from  its  compound  with  sulphur. 

28.  Portland  Cement.     General  Characteristics. — This  material 
having  been  perfected  within  recent  years,  has  many  important 
uses.     It  is  supplied  commercially  in  a  very  finely  ground  state, 


INTRODUCTORY.     ENGINEERING  MATERIALS  25 

and,  when  mixed  with,  water  alone,  or  when  mixed  with  water  and 
definite  proportions  of  sand,  gravel,  or  broken  stone,  it  can  be 
moulded  to  any  form  desired  and  will  gradually  harden  in  air  or 
under  water  in  the  form  to  which  it  is  moulded.  When  used  in 
this  way  it  is  popularly  known  as  concrete  or  beton. 

29.  Varieties  of  Lime  and  Cement. — The  many  forms  of  lime  and 
building  cement  consist  mostly  of  calcium  oxide   (CaO),  which  is 
formed  from  calcium  Carbonate   (CaC03)   by  calcination.     These 
forms  merge  one  into  another  according  to  the  kinds  and  amounts 
of  other  substances  mixed  with  the  lime',  and  their  variety  is  infinite. 

30.  True  Cements. — When  limestone  (CaC03)  contains  clay,  the 
process  of  calcination  produces  a  compound  which,  due  to  the  silica 
in  the  clay,  gives  the  product  the  power  of  solidifying  or  "  setting  " 
when  wet,  either  under  water  or  in  the  open  air.     The  degree  of 
heat  employed  in  the  calcining  process,  and  the  relative  proportions 
of  clay  and  limestone,,  determine  whether  the  product  is  hydraulic 
lime,  quick-setting  cement,  or  Portland  cement.     These  cements 
were  calcined  formerly  from  deposits  of  the  constituent  materials 
just  as  they  were  found   mixed   in  the  earth,   and  the   varieties 
of  these  mixtures  were  such  that  the  resulting  cements  were  not 
uniform,  but  the  application  of  chemistry  within  recent  years  for 
the  purpose  of  securing  exactly  the  amount  of  each  material  re- 
quired, and  of  avoiding  deleterious  materials,  has  brought  about 
the  extensive  manufacture  of  a  high  grade  of  Portland  cement. 
This  has  for  most  uses  displaced  other  kinds  of  building  cement, 
but  has  not  displaced  the  use  of  lime  for  mortar,  and  there  are 
cases  in  which  a  quicker  setting  cement  may  be  more  advantageously 
used  than  Portland  cement.    The  name  "  Portland  cement "  comes 
from  the  supposed  resemblance  of  the  dry  cement  to  Portland  stone, 
in  England,  and  was  given  it  by  its  discoverer,  in  1824. 

31.  Requisites   in   Selecting  Raw   Materials. — In   any  natural 
materials  chosen  for  the  manufacture  of  this  cement,  there  must  be 
ascertained : 

(1)  The  proportions  of  the  required  ingredients  contained. 

(2)  The  kinds  and  quantities  of  other  ingredients,  which  may 
be  harmful  in  quantity  or  because  of  their  chemical  action. 

32.  Composition  of  Cement. — It  is  now  established  that  the  essen- 
tial raw  ingredients  of  Portland  cement  are  limestone,  75  to 


26  MECHANICAL  PROCESSES 

and  alumina  (A1203)  and  silica  (Si02)  20  to  25%.  The  alumina 
and  silica  are  commonly  found  combined  as  *  clay,  which  is  a  silicate 
of  aluminum  (Al2032Si02)  +  2H20.  All  cements  contain  other 
ingredients  due  to  the  essential  materials  not  being  pure  in  nature 
and  from  contact  with  fuel  in  calcination.  Some  of  these  acci- 
dental ingredients  may  improve  the  cement.,  others  are  inert  and 
harmless  except  that  they  exist  in  such  quantity  as  to  displace 
essential  ingredients,  and  others  are  positively  harmful,,  if  present 
in  quantity,  because  of  the  chemical  action  they  produce.  There 
are  accidental  ingredients  usually  amounting  to  about  5%,  but 
these  must  not  include  over  1.75%  anhydrous  sulphuric  acid  (S03), 
nor  over  3%  of  magnesia  (MgO). 

Excess  of  clay  causes  a  cement  to  "  set "  quickly,  while  excess  of 
lime  causes  it  to  "  set "  slowly  or  imperfectly.  Iron  oxide  gives 
cement  its  color.  Portland  cement  is  improved  in  dry  storage,  as 
any  excess  of  lime  particles  are  air  slaked. 

33.  Manufacture  of  Portland  Cement. — A  cement  manufacturing 
plant  is  usually  located  at  or  near  a  natural  deposit  of  the  materials 
composing  cement.  These  materials  may  or  may  not  be  a  natural 
mixture,  but  in  either  case  chemical  analyses  must  be  made  to  de- 
termine, (1)  the  per  cent  of  lime,  (2)  the  per  cent  of  clay,  and  (3) 
the  per  cent  and  kind  of  other  ingredients.  This  analysis  deter- 
mines the  fitness  of  the  deposit  for  cement  manufacture.  With  a 
cement  plant  established,  the  essential  steps  in  manufacture  are : 

(1)  Chemical  analysis  in  the  laboratory  to  determine  the  correct 
proportion  of  lime  and  of  clay  for  making  up  a  kiln  charge. 

(2)  Grinding  the  properly  proportioned  ingredients  to  a  very 
fine  state,  which  also  accomplishes  their  thorough  mixture.     These 
may  be  coarsely  ground  before  mixing,  but  must  be  ground  after 
mixing  sufficient  to  pass  through  a  sieve  of  about  900  meshes  to  the 
square  inch.     Lack  of  proper  grinding  may  cause  the  cement  to  be 
worthless. 

(3)  Burning  the  ground  materials  to  a  state  of  incipient  fusion, 
to  change  their  chemical  composition.       This  is  done  in  a  long, 
cylindrical  kiln,  built  of  iron  plate,  lined  with  refractory  brick  and 

*  The  relative  proportions  of  silica  and  alumina,  as  compared  with  the 
limestone  in  cement,  are  found  by  Messrs.  Newberry  from  the  formula 
Wt.  of  limestone  —2. 8 Xwt.  of  silica+l.lXwt.  of  alumina. 


INTRODUCTORY.     ENGINEERING  MATERIALS  27 

mounted  to  revolve  on  its  axis  at  a  slight  inclination  to  the  horizon- 
tal. The  ground  mixture  is  introduced  wet  or  dry  at  the  higher 
end,  and  the  fuel  oil,  gas,  or  powdered  coal,  is  blown  in  at  the  lower 
end  v/here  it  ignites  in  a  flame  maintained  by  the  continuous  intro- 
duction of  fuel.  The  finely  divided  cement  material  is  gradually 
dehydrated  and  deprived  of  its  carbon  dioxide  as  it  is  tumbled  by 
the  slowly  revolving  kiln,  presenting  every  part  of  the  mass  to  the 
heat,  and  is  finally  vitrified  at  a  white  heat  into  small  clinkers  vary- 
ing in  size  from  that  of  a  pea  to  that  of  a  walnut.  These  clinkers 
are  kept  from  fusing  by  being  tumbled  from  the  lower  end  of  the 
kiln  at  the  proper  time.  Their  continuous  falling  from  the  kiln  is 
due  to  the  kiln's  inclination  and  slow  revolution. 

(4)  Grinding  the  clinker  to  a  fine  powder.  This  is  done  in  two 
operations.  The  first  grinding  is  done  between  millstones,  or  in  a 
revolving  cylinder  containing  steel  balls  about  6"  in  diameter.  The 
pulverizing  is  then  accomplished  by  machines  for  the  purpose,  in 
one  form  of  which  the  cement  is  fed  into  one  end  of  a  revolving 
cylinder  partly  filled  with  flint  stones  about  as  large  as  walnuts. 
The  pulverized  cement  issues  from  the  other  end  of  the  cylinder. 
It  must  be  ground  so  fine  that  not  more  than  8%  of  its  weight 
will  fail  to  pass  through  a  sieve  of  no.  100  mesh  (100  x  100  meshes 
per  square  inch). 

34.  Uses  of  Portland  Cement. — Cement  mixed  with  water  is  vir- 
tually a  plastic  stone,  and  it  can  be  used  for  many  purposes  in  place 
of  stone  with  economy  in  shaping  to  the  form  required,  and  advan- 
tage in  securing  a  hard,  fire-proof  material.  It  may  be  used  for 
shop  floors,  buildings,  foundations  for  heavy  machinery,  bridge 
piers,  walks,  waterworks  dams,  reservoirs,  walls,  dry-docks,  culverts, 
etc.  A  concrete  casing  will  protect  iron  or  timber  structures  from 
corrosion  in  air  or  in  water,  and  will  protect  exposed  iron  work  of 
structures  from  effects  of  conflagration. 

Strengthened  with  iron  bars,  or  meshed  wire,  placed  in  it  when 
it  is  being  moulded  to  shape,  it  is  known  as  re-enforced  concrete, 
and  will  thus  form  bridge  floors,  bridge  spans,  and  the  upper  floors 
of  buildings  which  must  support  great  weight. 

In  marine  use,  concrete  is  limited  because  of  its  weight.  It  may 
be  used  as  permanent  ballast  in  the  bilges  of  steel  ships,  and  is  an 
effective  protection  from  corrosion  when  applied  to  absolutely  clean 


MECHANICAL  PROCESSES 


iron  or  to  iron  surfaces  covered  with  closely  adhering  red  rust. 
When  so  used,  cement  may  be  mixed  with  water  and  applied  with 
a  brush,  or  it  may  be  mixed  in  the  proportion  of  about  two  parts 
sand  and  one  part  cement  and  applied  wet,  with  a  trowel,  in  a 
layer  varying  from  %  incn  to  any  thickness  desired.  In  this  way 
ships'  tanks,  bunkers,  and  bilges  are  protected,  as  the  mixture 
forms  a  close  bond  with  the  iron.  In  no  case  will  this  bond  form  if 
the  iron  is  oil  coated. 

35.  Cement  Mixtures. — Cement  and  water  alone  are  known  as 
"  neat "  cement,  and  are  seldom  so  employed  except  where  economy 
is  not  considered,  or  for  purposes  of  maximum  strength. 

For  most  purposes  a  mixture  of  sand,  broken  stone,  and  cement 
gives  ample  strength,  and  is  far  more  economical  than  the  use  of 
cement  alone. 

The  following  table  of  parts  by  volume,  gives  various  concrete 
mixtures : 


No. 

Portland 
Cement. 

Sharp 
Sand. 

Broken 
Stone. 

Uses. 

1 

1 

2 

4 

Highest  grade  of  miscellaneous  work. 

2 

J 

3 

6 

For  largest  building  foundations. 

3 

1 

4 

8 

For  ordinary  construction. 

4 

1 

4 

10 

For  economical  construction. 

In  these  mixtures,  the  broken  stone  merely  fills  space,  and  if  not 
available,  the  proportions  of  cement  and  sand  should  remain  as 
given. 

The  sand  also  fills  space,  saving  cement,  and  for  strength  it  is 
essential  that  enough  cement  be  used  to  surround  entirely  each 
grain  of  sand  and  thus  form  a  perfect  bond  between  cement  par- 
ticles. Broken  stone  and  sharp  sand  present  corners  and  angles 
for  the  better  attachment  of  cement,  as  claimed  by  some  users,  but 
beach  sand,  the  grains  of  which  have  been  washed  round  by  the 
sea,  and  rounded  pebbles,  are  also  frequently  used  with  cement, 

36.  Method  of  Using  Concrete. — For  shaping  concrete  to  a  form 
required,  the  usual  practice  is  to  make  a  form  of  planks  or  timbers, 
well  braced,  enclosing  the  space  which  the  concrete  is  to  occupy. 
The  mixture  is  carefully  made  in  a  mixing  machine  or  by  men  with 


INTRODUCTORY.     ENGINEERING  MATERIALS  29 

shovels,  wet  with  clean  water  to  a  mushy  consistency,  deposited  and 
tamped  in  place.  Sea  water  has  not  an  adverse  effect  on  Portland 
cement  of  good  quality.  When  once  wet,  the  mixture  must  be 
promptly  placed  in  the  form,  as  it  will  "  set "  in  an  hour  or  less. 
After  setting,  the  mass  is  at  first  very  weak  and  may  be  crumbled 
by  pressure  of  the  hand,  but  if  left  undisturbed  it  gradually  hardens 
to  the  consistency  of  stone,  requiring  months  or  years  for  reaching 
final  limit  of  hardness.  In  setting  and  for  a  few  hours  afterward, 
the  mixture  must  be  kept  wet.  In  extensive  work,  where  a  form 
cannot  be  filled  in  one  day,  the  upper  surface  is  left  rough  at  the 
end  of  each  day's  work  to  give  a  suitable  surface  for  the  close 
bonding  of  the  mixture  deposited  the  following  day. 

When  concrete  is  dumped  into  a  form  submerged  in  water,  it  is 
essential  that  the  mixture  be  subjected  to  as  little  wash  as  possible 
for  the  fine  particles  of  the  different  materials  composing  the  ce- 
ment must  be  thoroughly  mixed,  and  these  must  form  unbroken 
contact  throughout  the  interstices  of  the  sand  and  stone  in  order 
to  insure  a  solid,  well  bonded  mass  after  setting. 

Concrete  work  is  practically  impervious  to  water,  but  not  abso- 
lutely so  in  all  cases. 

37.  Causes   of   Setting    and   Strengthening    of   Cement. — It   is 
thought  that  the  setting  of  cement  is  due  to  the  crystallizing  of  the 
silicate  and  aluminate  of  lime,  which,  in  their  dry  and  anhydrous 
form  after  burning,  are  soluble  in  water,  but  which  pass  into  the 
hydrated  state  when  sufficiently  wet,  in  which  state  they  are  insolu- 
ble. 

The  hardening  after  setting  is  due  to  a  continued  crystallization 
of  salts  from  solution,  accompanied  by  other  chemical  and  physical 
changes  which  occur  very  slowly  and  which  are  not  well  understood. 

38.  Wood.    Use  as  Parts  of  Machinery. — Very  little  wood  is  now 
used  as   engine  or  machinery  parts.     Metal  has   displaced  wood 
almost  entirely  in  moving  and  stationary  parts  of  machines,  and  in 
many  general  uses  for  which  wood  was  once  exclusively  employed. 
The  present  highly  developed  industry  of  pressing  sheet  metal  to 
many  forms  more  or  less  intricate  has  made  it  possible  to  substitute 
metal  for  wood  in  furniture,  house  and  ship  trimmings,  automobile 
body  fittings,  utensils  and  many  other  articles. 

3 


30 


MECHANICAL  PROCESSES 


However,  wood  remains  a  very  useful  structural  material,  and  is 
particularly  of  value  in  engineering  needs  as  a  material  for  making 
patterns  of  objects  to  be  cast  in  metal,  as  will  be  seen  in  Chapter 
VIII. 

Wood  is  used  for  decks  and  sheathing  of  ships,  and  for  many 
parts  in  ship  equipment.  About  the  only  important  use  remaining 
for  it  in  marine  machinery  is  as  bearings  for  propeller  shafting. 
These  bearings  support  that  part  of  the  shafting  between  the  pro- 
peller and  the  body  of  the  ship.  They  cannot  be  given  care  or  atten- 
tion except  when  the  vessel  is  in  dry  dock,  and  are  lubricated  en- 
tirely by  the  water  in  which  the  vessel  floats.  Lignum  vitae,  a 
tropical  wood,  is  used  for  this  purpose. 

39.  Lumber  and  Timbers. — Wood  for  general  uses  is  handled  com- 
mercially in  the  form  of  lumber  or  timbers.  Trees  are  felled,  and 


FIG.  2. 


FIG.  3. 


that  part  of  the  lower  trunk  free  of  large  limbs  is  sawed  into  logs 
usually  a  few  inches  longer  than  an  even  number  of  feet.  These 
logs  are  hauled  to  the  sawmill  and  sawed  into  widths  and  thick- 
nesses as  required. 

The  log  end  in  Fig.  2  is  numbered  to  show  the  consecutive  cuts 
in  the  usual  method  of  sawing.  Most  of  these  are  tangential  cuts, 
i.  e.,  more  nearly  perpendicular  than  parallel  to  the  radius  of  the 
log  end.  Pieces  20  and  21  are  known  as  quarter-sawed  pieces,  as 
their  width  is  cut  along  the  radius  of  the  log  end.  Tangential  cuts 
are  cheaper  because  of  less  handling  on  the  saw  carriage  and  less 


INTRODUCTORY.     ENGINEERING  MATERIALS  31 

waste  of  the  log  material,  but  lumber  from  these  cuts  warps  more, 
is  less  durable,  and  does  not  show  the  fineness  ©f  grain  when  com- 
pared with  quarter-sawed  lumber.  The  upper  half  of  Fig.  3  shows 
a  method  of  getting  more  quarter-sawed  cuts  from  a  log  than  are 
obtained  in  Fig.  2  without  greatly  increasing  the  cost  of  cutting. 
The  log  is  quartered  and  each  quarter  is  sawed  into  pieces  as  con- 
secutively numbered,  quadrant  A  giving  two  quarter-sawed  pieces, 
1  and  2,  and  two  pieces,  3  and  9,  which  are  nearly  quarter  sawed. 
Quadrant  B  shows  another  method  of  sawing,  giving  pieces  3  and 
11,  quarter  sawed,  and  but  one  piece,  No.  10,  corresponding  to 
pieces  N"os.  3  and  9  of  quadrant  A.  True  quarter  sawing  is  shown 
in  quadrant  D,  and  approximate  quarter  sawing,  with  less  waste, 
is  shown  in  quadrant  C?  of  Fig.  3. 

40.  Lumber  Grading, — The  several  pieces  sawed  from  a  log  are 
not  of  the  same  quality,  but  vary  more  or  less  in  grade.    The  slabs, 
covered  on  one  side  with  bark,  and  the  culls  or  very  unsound  pieces, 
are  of  no  value  as  lumber.     The  ungraded  lumber  from  a  log  is 
known  as  log  run.     In  large  mills,  log  run  is  graded  as  to  quality 
after  it  is  finally  sent  from  the  saw  on  roller  conveyors  and  the  sev- 
eral grades  are  stacked  separately  in  such  a  way  as  to  allow  ready 
access  of  air  for  seasoning  and  to  shed  rain.     After  drying,  and 
when  removing  it  from  the  stacks  for  shipping,  the  lumber  is  further 
subject  to  an  adopted  form  of  inspection,  in  which  each  piece  is 
graded  for  the  purchaser's  acceptance. 

41.  Hard  and  Soft  Wood  Lumber. — Hard  woods  are  those  cut 
from  the  broad-leaf  trees  (as  oak,  hickory,  poplar),  and  soft  woods 
are  those  from  the  conifers,  or  needle-leaf  trees  (as  pine,  cedar,  fir 
and  redwood). 

42.  Heart  and  Sap  Wood. — The  wood  surrounding  the  center  of 
a  tree  is  heart  wood  and  outside  of  this  is  the  sap  wood,  usually 
lighter  in  color  than  the  heart.     Sap  wood,  except  in  certain  trees, 
as  ash  and  hickory,  is  less  hard  and  durable  than  heart  wood. 
However  when  the  heart  wood  at  the  center  of  the  tree  is  exposed 
in  the  surface  of  a  board,  it  tends  to  split  away  from  the  board. 
The  amount  of  sap  or  heart  wood  in  a  piece  of  sawed  timber  may 
be  seen  by  the  difference  in  color  of  the  sawed  surface,  also  end 
inspection  will  show  from  which  part  of  the  tree  the  piece  is  taken. 


32  MECHANICAL  PROCESSES 

In  Fig.  4  the  large  radii  of  curvature  of  the  rings  show  these  as 
sap  pieces,  the  points  A   being  nearest  the  bark.     Fig.   5  shows 


FIG.  4. 


FIG.  5. 


heart  pieces,  indicated  by  the  curvature  of  the  rings.    The  heart  of 
the  tree  is  at  B. 

43.  Lumber  Inspection  Rules. — For  uniformity  in  lumber  sizes 
and  qualities,  certain  general  rules  are  adopted  by  lumber  pro- 
ducers, who  adopt,  also,  specific  rules  for  the  inspection  of  each 
kind  of  wood  according  to  its  uses.  Lumber  rules  are  subject  to 
changes  particularly  because  of  the  increasing  scarcity  of  wood. 

(1)  Standard  lumber  lengths  are  6,  8,  10,  12,  14,  and  16  feet, 
though  6-  and  8-foot  lengths  are  for  special  uses.    Boards  measur- 
ing an  odd  number  of  feet  are  classed  with  the  next  lower  even 
lengths,  unless  specified  otherwise. 

(2)  Standard  thicknesses  are  %,  %,  %,  %,  1,  1*4,  1V2,  2,  2%, 
3,  and  4  inches.     Pieces  larger  than  4x4  inches  are  called  timbers. 

(3)  The  standard  qualities  or  grades  for  hardwoods  are,  usually, 
firsts,  seconds,  and  one  or  more  grades  of  common.    Soft  woods  are 
graded  according  to  their  uses.    An  inspector  determines  the  grade 
to  which  any  piece  of  lumber  belongs  by  its  width,  amount  of  heart 
or  sap,  and  defects  affecting  its  strength  and  appearance. 


INTRODUCTORY.     ENGINEERING  MATERIALS  33 

(4)  Inspection  is  usually  made  of  the  worst  side  of  the  board, 
and  warps  are  always  considered  as  defects. 

It  is  not  uncommon  for  purchasers  of  large  amounts  of  lumber 
to  have  their  own  specifications  for  the  general  inspection  of  lumber. 

44.  Standard  Defects. — An  example  of  the  standardization  of 
lumber  defects  is  given  by  the  following  copy  of  Navy  Department 
General  Lumber  Specifications.     Each  one  of  the  following  items 
constitutes  a  standard  defect : 

(a)  One  sound  knot,  114  inches  in  diameter,  called  a  standard 
knot. 

(&)  Two  knots  not  exceeding  in  extent  or  damage  one  standard 
knot. 

(c)  Wormholes,  grub  holes,  or  rafting-pin  holes  not  exceeding 
in  extent  or  damage  one  standard  knot. 

(d)  Heart  centers,  shakes,  rot,  or  dote  not  exceeding  in  extent 
or  damage  one  standard  knot. 

(e)  Splits  which  do  not  exceed  12  inches  in  length  in  firsts,  nor 
one-sixth  the  length  of  the  piece  in  seconds.    Not  more  than  25  per 
cent  of  the  whole  number  of  pieces  in  each  grade  may  be  so  split. 

NOTE. — Wide  pieces  of  lumber  that  would  take  two  or  three 
standard  knots  may  have,  if  properly  located,  one  large  knot,  equal 
to  two  or  three  standard  knots,  if  there  are  no  other  defects. 

Shakes  are  splits  in  the  end  of  a  board  due  to  seasoning,  generally 
occurring  before  the  board  is  cut  from  the  log. 

Checks  are  cracks  showing  in  the  surface  of  a  board,  due  to  sea- 
soning, and  are  sometimes  large  enough  to  be  defects. 

Dote  is  unsoundness  due  to  decay. 

Wane  is  the  beveled  or  bark-covered  edge  of  a  board. 

45.  Rough  and  Dressed  Lumber. — All  lumber  direct  from  the 
saw  is  rough  lumber.     After  seasoning,  the  better  grades  may  be 
re-sawed  into  smaller  pieces  and  are  frequently  planed  smooth,  on 
one  or  both  faces  and  one  or  both  edges,  by  machinery,  before  mar- 
keting.    Lumber  thus  planed  is  said  to  be  dressed,  and  is  sold  at 
the  width  and  thickness  it  had  when  rough.    Examples  of  designa- 
tions of  dressed  lumber  are  as  follows:     SIS  means  surfaced  (or 
dressed)  on  one  side;  S1S1E  means  surfaced  on  one  side  and  one 
edge;  S2S2E  means  surfaced  on  both  sides  and  both  edges. 


34  MECHANICAL  PROCESSES 

46.  Lumber  Measurement. — Lumber  and  timbers  are  measured 
and  sold  by  board  feet.     A  board  foot  has  a  surface  12  x  12  inches 
and  a  thickness  of  one  inch.     Boards  less  than  an  inch  in  thick- 
ness are  regarded  as  an  inch  thick  in  selling,  but  those  of  any  frac- 
tion over  an  inch  are  sold  for  what  they  actually  contain. 

A  specimen  bill  of  lumber  is  as  follows: 

(1)  40  p.  2    x    6x16 

(2)  12  p.     Jx    8x12 

(3)  80  p.  IJx    6x16 

(4)  30  p.  1    X  12x14 

Written  in  full,  the  first  item,  for  example,  reads  40  pieces  2 

inches  thick,  6  inches  wide,  16  feet  long. 

The  board  feet  in  the  2d  and  3d  items  are  as  follows : 

fn  item  (2),  each  piece  is  regarded  as  having  a  thickness  of  one 

inch.    The  surface  of  one  piece  in  square  feet  is  T82-  X  12 ;  hence  the 

item  has  a  total  of  12_xlx8x  12  =  96  board  ft. 

1/& 

In  item  (3),  the  surface  of  each  piece  is  -f-%  x  16  sq.  ft.,  hence  the 
item  has  a  total  of  80  X  f  X  A  X  16  =  960  board  ft. 

47.  Durability  of  Wood. — Wood  may  be  preserved  indefinitely  if 
kept  dry  or  submerged  in  still  water,  and  free  from  attacks  of  in- 
sects.   Wood  exposed  to  the  atmosphere  absorbs  more  or  less  moist- 
ure.    Alternate  wetting  and  drying,  very  common  with  posts  or 
poles  where  they  enter  the  ground,  is  an  active  means  of  decay. 
The  best  preserved  wood  is  that  buried  in  wet  or  damp  earth,  ex- 
cluded from  air  and  insects.    Timbers  preserved  in  this  way  have 
remained  sound  for  centuries. 


CHAPTEE  II. 
A  GENERAL  OUTLINE  OF  METAL-PRODUCING  PROCESSES. 

48.  Ores. — The  common  metals,  excepting  copper,  do  not  occur 
free  in  nature,  but  are  produced  from  their  ores  which  generally 
require  chemical  treatment  at  high  heat  in  furnaces.     Uncomhined 
copper,  known  as  "  native  "  copper,  mixed  with  more  or  less  earthy 
material,  is  found  in  some  parts  of  the  world,  notably  in  the  Lake 
Superior  region,  but  the  main  source  of  all  engineering  metals  is 
their  ores,  which  are  more  or  less  abundantly  distributed  over  the 
earth. 

An  ore  is  a  natural  substance  composed  of  a  metal  chemically 
combined  with  one  or  more  non-metallic  substances.  Ores  of  differ- 
ent metals  are  sometimes  found  incorporated  in  the  same  mass, 
and  almost  all  ores  are  found  mixed  with  impurities  of  a  non- 
metallic  nature,  as  rock,  sand,  clay,  etc.,  known  in  mining  as 
gangue.  Many  ore  deposits  within  range  of  easy  transportation  can- 
not be  profitably  worked  either  because  of  excessive  gangue  or 
because  of  chemical  composition  of  ore  or  gangue  which  renders 
smelting  unprofitable. 

49.  Elimination  of  Gangue. — As  an  ore  comes  from  the  mine  it  is 
desirable  to  eliminate  at  once  the  gangue.    This  may  be  done  more 
or  less  successfully  with  some  ores  by  simple  hand-picking  methods, 
while  other  ores  must  be  crushed  in  a  stone  breaker  or  stamp  mill, 
and  the  gangue  eliminated  from  the  finely  crushed  mass  by  dress- 
ing, which  consists  of  passing  running  water  over  the  mass  in  a 
succession  of  boxes  so  that  the  current  will  carry  the  lighter  par- 
ticles to  the  lower  boxes  while  the  heavier  particles  settle  in  the 
upper  boxes.    There  are  ores  from  which  the  gangue  cannot  be  re- 
moved except  in  furnace  processes,  and  some  ores  have  too  little 
gangue  to  need  preliminary  separation. 

Some  ores  are  subjected  to  weathering.  They  are  heaped  in  the 
open  air  and  left  exposed  to  sun  and  rain  for  weeks  or  months. 


36  MECHANICAL  PROCESSES 

This  disintegrates  the  lumps  and  washes  away  soluble  salts  and 
much  powdered  gangue. 

50.  Calcination. — Another  method  of  reducing  the  quantity  of 
impurity  before  the  ore  is  transported  from  the  mine  is  by  calcina- 
tion, which  consists  of  heating  the  ores  to  a  point  short  of  fusion. 
This  drives  away  moisture  and  some  combined  sulphur,  and  breaks 
up  carbonates,  changing  them  to  oxides  by  driving  off  C02.    Calcina- 
tion is  done  crudely  by  making  alternate  layers  of  fuel  and  ore  on 
the  ground  and  lighting  the  fuel,  but  more  effective  methods  are 
to  confine  the  ore  and  fuel  by  walls,  or  still  better  by  kilns,  in 
which  the  heat  is  more  intense  and  more  uniformly  distributed. 

After  calcining,  the  ore  is  ready  for  transportation  to  the  smelter, 
which  is  usually  located  away  from  the  mines  for  the  convenience 
of  obtaining  fuel  and  labor. 

51.  Breaking  up  the  Ore  Compound. — The  actual  metallurgical 
operation  of  breaking  up  the  chemical  combination  of  metal  with 
oxygen  and  with  other  elements  in  ores  is  done  by  heat  in  furnaces 
and  is  called  the  dry  process;  or  is  done  by  making  a  solution  of  the 
metallic  compounds  and  breaking  up  these  by  chemical  re-agents, 
known  as  the  wet  process  or  leaching. 

Smelting,  as  used  in  the  dry  process,  is  the  operation  of  fusing 
ores  by  heat  in  suitable  furnaces.  This  is  an  essential  step  of  metal 
extracting,  and  its  meaning  is  usually  broadened  to  include  all 
steps  of  the  process  of  heat  extraction  of  metals. 

Reduction  is  the  separation  of  a  metal  from  its  oxide,  though 
usually  applied  to  the  separation  of  a  metal  from  any  ore,  whether 
oxide  or  not. 

Roasting  is  the  heating  with  free  access  of  air  in  order  to  change 
the  ore  partly  or  entirely  to  an  oxide  for  reduction  later  on. 

The  processes  of  extracting  most  of  the  common  metals  from 
their  ores  are  complicated  because  of  the  several  chemical  changes 
necessary  to  extract  the  metal  in  a  sufficiently  pure  state  for  use. 
The  different  chemical  compositions  of  ores,  their  various  grades 
due  to  the  relative  per  cents  of  metal  and  of  other  ingredients  con- 
tained, and  the  existence  frequently  of  two  or  more  metals  in  the 
same  ore  mixture,  make  the  treatment  of  most  ores  very  varied  and 


GENERAL  OUTLINE  OF  METAL-PRODUCING  PROCESSES        37 

complex.  By  far  the  greater  quantity  of  metals  is  produced  by  the 
dry  process,  and  iron  is  very  easily  produced  because  its  oxide  ores 
are  abundant  and  are  smelted  by  the  single  process  of  reduction. 

The  treatment  of  ores  of  copper,  zinc,  lead,  tin,  nickel  and  anti- 
mony is  more  difficult.  The  object  of  each  step  in  the  processes 
of  extracting  a  metal  from  its  ores  is  to  simplify  the  ore  com- 
pound. This  is  done,  as  has  been  outlined  in  part,  by  (1)  sep- 
arating the  ore  from  the  gangue  (par.  49),  (2)  driving  away  cer- 
tain ingredients  by  a  heat  short  of  fusion  (par.  50),  and  (3) 
fusing  the  ore  one  or  more  times  in  the  presence  of  certain  re-agents 
called  fluxes  which  combine  with  the  non-metallic  substances  and 
allow  the  liberated  metal  to  separate  and  settle  in  an  impure  state. 
A  metal  thus  obtained  in  the  impure  state  must  be  refined  before  it 
is  used. 

52.  Smelting  Furnaces. — The  step  of  the  process  named  in  item 
(3)  of  the  preceding  paragraph  is  that  of  smelting,  and  is  usually 
carried  on  in  furnaces  built  of  common  silica  brick  for  the  outer 
layers,  and  high  grade  refractory  brick  for  the  inner  layers.     This 
brick  work  is  either  incased  in  a  shell  of  iron  plates,  or  is  held  to- 
gether by  iron  bands  and  rods,  which  are  wholly  on  the  outside  of 
the  furnace  and  do  not  enter  the  fire  space.     There  are  several 
modifications  of  furnaces  for  smelting  ores  of  different  metals,  but 
all  smelting  furnaces  are  included  in  the  two  general  types  of  this 
class,   namely,   the   blast  furnace  and   the  reverberatory  furnace. 
These  must  be  strongly  built  on  permanent  foundations,  and  must 
be  able  to  stand  the  intense  heat  of  the  operation. 

53.  The  Blast  Furnace. — Fig.  6  shows  the  essential  parts  of  a 
blast  furnace  for  smelting  iron.     It  is  given  the  name  of  blast 
furnace  because  combustion  is  maintained  by  forcing  a  blast  of  air 
through  the  mass  of  fuel,  ore  and  flux  which  completely  fills  the 
furnace.    This  type  of  furnace  is  vertical  so  that  gravity  may  assist 
in  disposing  of  the  fused  products.     The  main  point  of  difference 
from  the  reverberatory  furnace  is  that  ore  and  fuel  are  mixed  in 
the  blast  furnace  and  are  kept  separate  in  the  reverberatory  furnace. 


38 


MECHANICAL  PROCESSES 


Figs.  6a  and  6b  are  two  views  of  the  outside  of  a  blast  furnace. 
They  are  lettered  to  agree  with  the  description  given  for  Fig.  6. 


FIG.  6. — Blast  Furnace. 


The  parts  of  this  furnace,  shown  in  Fig.  6,  are  designated  as 
follows,  viz. : 

S.  Shaft.  This  extends  from  the  top  down  to  the  part  of  largest 
diameter. 


GENERAL  OUTLINE  OF  METAL-PRODUCING  PROCESSES        39 

B.  Boshes.  This  is  the  tapered  portion  below  the  shaft.  Built 
in  with  the  brick  work  of  the  boshes  are  many  hollow  wedge-shaped 
segments  of  copper.  These  segments  are  placed  with  alternate  seg- 
ments of  bricks  to  encircle  the  boshes,  and  many  layers  of  this  con- 
struction make  up  the  walls  of  the  boshes.  These  copper  segments 
are  known  as  "  bosh  plates."  Some  of  them  are  marked  P  in  Fig. 
6a.  Water  is  circulated  through  each  bosh  plate,  by  a  system  of 
external  piping,  to  allay  the  intense  heat  at  that  part  of  the  furnace 
and  thus  prevent  injury  to  the  bosh  walls.  The  bosh  plate  edges 
do  not  extend  in  quite  so  far  as  does  the  brick  work,  and  are  pro- 
tected by  a  covering  of  clay.  If  a  plate  becomes  clogged  by  sedi- 
ment from  the  circulating  water,  or  if  its  inner  edge  is  melted  or 
damaged,  it  can  be  pulled  out  and  replaced  by  a  new  plate  by  re- 
ducing the  blast  pressure  while  this  work  is  in  progress. 

Y.  Tuyere  holes.  These  openings  conduct  into  the  furnace  the. 
air  of  the  blast.  Fig.'  6  has  eight  tuyere  holes.  The  tuyeres  are  metal 
tubes  leading  from  the  blast  main  into  the  furnace  through  the 
tuyere  holes.  Tuyeres  are  not  shown  in  Fig.  6,  and  the  horizontal 
portion  (or  tuyere  proper)  is  disconnected  and  removed  in  Fig.  6a. 
Each  tuyere  is  surrounded  by  a  helix  of  pipe  through  which  water 
circulates  to  keep  the  end  of  the  tuyere  from  melting  in  the  furnace. 
Fig.  6a  shows  at  E  an  opening,  covered  by  a  mica  door  when  the 
furnace  is  in  use,  which  enables  the  furnace  man  to  see  the  interior 
of  the  furnace  through  the  tuyere  when  in  blast. 

M.  Hot  blast  main.  This  is  a  pipe  3  ft.  or  more  in  diameter, 
made  of  iron  plates  and  lined  inside  with  refractory  brick.  It  en- 
circles the  furnace,  delivering  highly  heated  air  from  the  blast  stove 
to  the  tuyeres. 

//.  Hearth.  This  is  the  part  of  the  furnace  below  the  line  of 
tuyere  holes  which  receives  molten  slag  and  metal,  and  when  the 
slag,  which  floats  on  the  metal,  reaches  the  height  of  the  cinder 
notch  C,  it  is  drawn  off. 

T.  Tapping  hole.  Metal  is  tapped  from  the  hearth  through  this 
hole.  In  tapping,  an  iron  bar  is  used  to  dig  out  the  clay  plug  stop- 
ping the  hole,  and  when  the  metal  has  run  out,  another  plug  is 
forced  in  to  stop  the  hole,  by  means  of  the  ram  U  (known  as  the 
"  mud  gun  ")  swung  from  the  small  crane  W. 


40  MECHANICAL  PROCESSES 

G.  Gas  main  or  "  down  comer/'  a  brick-lined  pipe  leading 
away  the  gaseous  products  of  the  blast  and  delivering  them,  through 
the  dust  catcher,  to  the  gas  main,  Q,  which  distributes  them  to  the 
blast  stoves. 

J.  Shaft  lining.  This  lining  is  of  highest  quality  refractory 
brick  (fire  clay)  laid  in  a  mortar  of  fire  clay.  The  lining  can  be 
renewed  when  worn  out.  The  double  hatched  lining  below  the 
tuyere  holes  in  Fig.  6  is  not  subject  to  excessive  wear. 

D.  Silica  brick  body,  in  Fig.  6.  The  furnace  body  is  encased  in 
plate  steel  marked  D  in  Fig.  6b. 

K.  Cone.  This  is  a  cone-shaped  hollow  cast  iron  ring  built  into 
the  top  or  "  throat "  of  the  furnace. 

L.  Bell,  a  cast  iron  cone  suspended  by  a  heavy  chain  from  the 
lever  N.  This  cone  closes  the  throat  of  the  furnace  and  is  opened 
for  admitting  materials  of  the  furnace  charge. 

R.  Stand  pipe.  Before  lowering  the  bell  to  admit  a  new  charge 
to  the  furnace,  the  lid  of  the  stand  pipe  is  raised  to  relieve  the  gas 
pressure  at  the  top  of  the  furnace.  This  obviates  the  escape  of  gas 
and  flame  from  the  furnace  throat. 

54.  Blast   Furnace  Modifications. — The  principle  of  the  blast 
furnace  as  shown  in  Fig.  6  is  applied  to  the  smelting  of  copper  and 
lead  ores,  but  the  furnaces  used  for  these  ores  are  somewhat  modi- 
fied.   Iron  smelting  furnaces  vary  from  50  to  100  ft.  in  height,  but 
copper  and  lead  furnaces  are  much  smaller  and  are  not  always  circu- 
lar in  cross  section.     In  copper  and  lead  furnaces  the  boshes  and 
at  least  part  of  the  shaft  have  merely  inner  and  outer  surfaces  of 
iron,   with   water   circulating   between   them.     This   water   jacket 
arrangement  is  necessary  as  the  oxides  of  these  metals  attack  a  fire 
brick  lining.    The  cooling  effect  of  the  water  is  such  that  the  inner 
surface  of  the  iron  jacket  becomes  covered  with  a  solidified  slag 
which  is  replaced  as  fast  as  it  wears  away. 

The  modifications  of  this  furnace  for  lead  and  copper  smelting 
are  due  to  the  differences  of  the  ores  of  these  metals  from  the  ores 
of  iron,  and  to  the  complexity  in  smelting  these  as  compared  with 
iron  smelting. 

55.  Acid  and  Basic  Ores. — The  earthy  matter  of  ores  consists 
mostly  of  silica  (sand),  silicate  of  aluminum  (clay),  limestone,  and 
magnesia.     All  of  these  are  seldom  found  in  the  same  ore,  but 


GENERAL  OUTLINE  OF  METAL-PRODUCING  PROCESSES        41 


almost  all  ores  contain  (1)  silica  and  silicate  of  aluminum,  or  (2) 
limestone  and  magnesia.  The  ores  containing  a  predominance  of 
the  materials  of  group  ( 1 )  are  acid  ores,,  and  those  containing  a  pre- 
dominance of  the  materials  of  group  (2)  are  basic  ores.  Acid  ores 
are  in  much  greater  abundance  than  basic  ores. 


FIG.  GA. — Base  of  a  Blast  Furnace. 
B — Boshes.  P — Bosh  plates. 

E — Peep  hole.  T — Tapping  hole. 

H— Hearth.  U — Mud  gun. 

M — Blast  main.  V — Water  valves  for  bosh  plates. 


W — Mud  gun  crane. 

Y — Tuyere  holes. 

Z — Furnace  supports. 


56.  Fluxes. — The  usual  operations  of  smelting  require  that  an  ore 
shall  always  be  mixed  with  a  flux.  The  ore  is  either  acid  or  basic, 
and  the  flux  must  be  either  basic  or  acid,  opposite  to  the  character 
of  the  ore.  At  the  temperature  of  the  furnace,  neither  the  acid 


42  MECHANICAL  PROCESSES 

nor  the  basic  substance  in  an  ore  will  melt,  and  in  order  to  melt 
and  dispose  of  it,  there  must  be  introduced  with  the  ore  a  certain 
amount  of  flux,  which  combines  chemically  with  the  earthy  sub- 
stances of  the  ore,  forming  slag.  At  the  temperature  of  the  fur- 
nace the  slag  is  molten,  and  when  slag  and  metal  collect  in  the 
hearth,  the  slag  floats  on  the  metal  and  protects  it  from  oxidation. 

The  materials  used  as  fluxes  in  smelting  are  (1)  silica  and  sili- 
cate of  aluminum  as  acid  fluxes,  and  (2)  limestone  and  magnesite 
(an  impure  magnesia)  as  basic  fluxes.  These  fluxes  are  the  same 
materials  as  those  found  with  ores  which  determine  their  acid  or 
basic  character,  hence  it  is  necessary  to  place  with  an  ore  the  flux 
opposite  in  character  to  that  which  the  ore  is  found  naturally  to 
contain. 

In  making  up  a  furnace  charge,  the  chemical  composition  of  the 
ore  must  be  determined  in  the  laboratory,  and  a  flux  must  be 
chosen,  in  kind  and  quantity,  which  will  unite  completely  with  the 
earthy  materials  of  the  ore.  Too  little  flux  will  not  take  up  all  the 
refuse  parts  of  the  ore,  and  too  much  will  act  in  disintegrating  the 
fire  brick  lining  of  a  furnace  in  spots  not  protected  by  a  slag  coat- 
ing. A  practical  smelter  can  judge  from  the  color  of  a  broken 
piece  of  cold  slag  whether  or  not  the  flux  is  in  sufficient  quantity, 
and  an  occasional  analysis  of  the  slag  is  a  beneficial  check.  Sulphur 
and  phosphorus  must  be  avoided  in  fluxes,  and  are  not  desirable  in 
ores. 

57.  Blast  Furnace  Operation. — This  description  applies  particu- 
larly to  iron  smelting,  but  it  is  also  the  essential  part  of  blast  fur- 
nace operation  for  smelting  other  ores.  The  starting  of  a  blast  fur- 
nace in  operation  is  called  "  blowing  in."  A  light  fire  is  started  in 
the  hearth  and  is  for  a  while  supplied  only  with  enough  fuel  to 
keep  it  going.  Care  must  be  taken  to  heat  up  and  dry  out  the 
furnace  very  slowly  to  avoid  cracks  in  the  newly  built  or  repaired 
parts,  or  in  the  slag  coating  which  acts  as  a  protection  to  the  fur- 
nace walls.  Very  gradually  the  quantity  of  fuel  is  increased  and 
when  it  is  above  the  tuyeres,  a  light  blast  is  started  to  increase 
combustion.  After  a  few  weeks,  with  a  large  iron  smelting  furnace, 
the  shaft  becomes  well  filled  with  fuel  and  the  heat  has  reached  a 
maximum. 

A  little  slag  from  the  slag  dump  is  now  added.  This  melts  and 
runs  down,  covering  the  bottom  of  the  hearth  and  keeping  it  hot, 


GENERAL  OUTLINE  OF  METAL-PRODUCING  PROCESSES       43 


FIG.  GB.— Top  of  a  Blast  Furnace. 

A — Charging  car.  G — Down  comer.  R — Stand  pipe. 

D — Furnace  shaft  casing.  N — Bell    lever. 


44 


MECHANICAL  PROCESSES 


The  tap  hole  is  stopped  with  clay.  Ore  and  flux  are  added,  the 
blast  pressure  is  increased  to  that  desired,  and  the  furnace  soon 
reaches  a  condition  of  maximum  output.  The  furnace  may  be  kept 
in  operation  for  months  without  cessation,  until  it  must  be  stopped 
for  relining  or  repairs.  When  in  operation,  the  furnace  is  charged 
at  intervals  of  a  few  minutes  with  a  layer  of  coke  and  then  a  layer 
of  flux  and  ore.  The  material  is  sprayed  with  water,  hoisted  to  the 


FIG.  7.— Blast  Furnaces  and  their  Hot  Blast  Stoves. 

top  of  the  furnace,  and  dumped  into  the  cone.  The  water  prevents 
the  carrying  of  an  excessive  amount  of  dust  from  the  furnace  into 
the  "  down  comer/'  In  Fig.  6b,  the  charging  car  A  has  just 
reached  the  top  of  its  track  and  is  about  to  be  automatically  dumped 
into  the  hopper  over  the  cone. 

The  air  blast  is  supplied  by  a  centrifugal  or  other  form  of  blower, 
and  is  forced  through  coils  of  heated  pipe  for  lead  and  copper,  or 
through  a  large  stove  (called  a  regenerative  or  hot-blast  stove)  for 


GENERAL  OUTLINE  or  METAL-PRODUCING  PROCESSES        45 

iron,  entering  the  furnace  at  a  high  heat  through  the  hot-blast  main 
and  tuyeres.  The  most  intense  heat  of  the  furnace  begins  im- 
mediately above  the  tuyeres  and  extends  up  as  far  as  the  oxygen 
lasts  for  the  complete  burning  of  the  fuel.  This  is  called  the  fusion 
zone. 

The  ore  heated  above  the  fusion  zone  disintegrates,  is  reduced, 
giving  up  its  gangue  to  the  action  of  the  flux,  and  as  it  sinks  into 
the  zone  of  fusion,  it  gradually  melts.  The  metal,  more  or  less 
impure,  trickles  to  the  hearth,  and  the  slag  also  runs  down,  float- 
ing on  top  of  the  metal.  When  the  slag  rises  to  the  level  of  the 
cinder-notch  it  runs  out,  and  the  metal  is  tapped  out  before  it  is 
high  enough  to  reach  the  cinder  notch.  Care  is  always  taken  to 
leave  a  covering  of  slag  over  the  metal.  The  slag,  drawn  off  at 
the  rear  or  side  of  the  furnace,  is  conveyed  along  a  trough  or  trench 
into  cars  with  sheet  steel  bodies,  and  is  hauled  away  and  dumped 
when  cool.  Slag  of  some  compositions  is  now  used  for  making  Port- 
land cement.  The  metal  is  tapped  several  times  during  each  day,  and 
is  conducted  from  the  furnace  along  a  trench  in  the  floor.  This 
trench  is  lined  with  a  mixture  of  sand  and  clay  which  is  baked  hard 
to  prevent  wearing  away  by  the  erosive  action  of  the  metal.  Fig.  16 
shows  metal  pouring  from  a  furnace,  and  Fig.  17  shows  the  ladles 
on  cars  to  receive  it. 

When  a  furnace  is  to  be  shut  down,  or  "blown  out,"  the  ore 
charge  is  gradually  reduced  and  stopped.  Flux  and  fuel  are  con- 
tinued until  all  metal  and  slag  are  tapped  out,  and  the  flux  is  then 
discontinued.  The  fuel  is  gradually  reduced,  the  blast  pressure  is 
lowered  and  finally  shut  off,  and  the  fire  slowly  burns  out.  The 
furnace  must  be  allowed  to  cool  gradually  before  being  emptied. 

58,  The  Blast  Stove. — In  blast  furnace  smelting  of  copper  and 
lead,  the  gases  passing  from  the  top  of  the  furnace  do  not  contain 
much  gas  which  will  burn,  hence  they  are  allowed  to  escape,  but  in 
the  iron  smelting  furnace  not  enough  oxygen  reaches  the  upper 
part  of  the  furnace  to  unite  with  all  the  incandescent  carbon  of  the 
fuel.  As  a  result  of  this,  much  C02  is  reduced  to  CO,  which  passes 
from  the  furnace  unburned.  To  let  this  gas  escape  into  the  atmos- 
phere would  be  a  considerable  loss  of  fuel,  hence  it  is  conveyed 
through  the  "  down-comer  "  and  dust  catcher  to  a  large  stove  called 
the  blast  or  regenerative  stove,  where  it  is  burned  to  heat  the 
4 


46 


MECHANICAL  PROCESSES 


brickwork  of  the  stove.  After  the  brickwork  has  become  very  hot, 
the  gas  is  shut  off  from  this  stove,  and  air  is  blown  through  to 
absorb  the  heat  on  its  way  to  the  blast  furnace  through  the  tuyeres. 


SE.CTION   A  A 


FIG.  8. — Hot  Blast  Stove  (Vertical  Section). 

In  this  way  the  blast  is  supplied  with  air  at  about  1400°  F.,  and 
the  intensity  of  the  furnace  heat  is  much  greater  in  the  fusion  zone 
than  if  cold  air  were  blown  in. 

Fig.  8  shows  a  form  of  blast  stove  used  for  this  purpose,  known 


GENERAL  OUTLINE  OF  METAL-PRODUCING  PROCESSES        47 


as  the  Calder  Stove.  Several  other  forms  of  stoves  are  used,  all 
operated  on  the  same  principle  and  differing  only  in  interior  ar- 
rangement. Fig.  7  shows  a  group  of  five  stoves  which  are  con- 


AiR  INLET 


AS  INLE1 
SECTION   B-B 
AIR   INLET 


CLEAN-OUT  DOOR 

NOTE: 

MADEOF9"e.l5>,"BRICK 

FIG.  SA. — Hot  Blast  Stove  (Horizontal  Sections). 

nected  to  their  common  chimney  P  by  an  underground  smoke  con- 
duit. The  stoves  are  made  of  an  outside  casing  of  steel  plates  and 
an  interior  lining  of  refractory  brick.  Brick  partitions  are  so 
placed  as  to  check  the  passage  of  air  and  gases. 


48  MECHANICAL  PROCESSES 

The  stove  in  Fig.  8  is  operated  as  follows :  Valves  connecting  the 
interior  space  of  the  stove  with  the  hot  and  cold  blast  mains  having 
been  closed,  the  chimney  damper  is  opened  and  gas  from  the  dust 
catcher  is  admitted  to  the  stove  through  the  gas  inlet  marked  in 
section  B-B,  of  Fig.  8a,  This  gas  is  hot  enough  to  burn  just  as  soon 
as  air  is  admitted  through  the  various  air  inlets,  which  are  regulated 
by  dampers.  Combustion  takes  place  in  the  two  large  vertical  spaces 
in  the  right  half  of  the  stove,  the  burned  gases  are  drawn  down- 
ward by  the  chimney  draft  through  the  small  vertical  spaces  into 
which  the  left  hand  part  of  the  stove  is  divided,  and,  following  the 
small  arrows,  enter  the  circular  conduit  through  openings  at  the 
bottom  of  the  stove.  In  passing  downward,  the  gases  give  up  much 
heat  to  the  brick  partitions,  and  finally  they  escape  through  the 
chimney  which  surmounts  the  stove.  After  about  an  hour  of  this 
operation,  the  brickwork  has  reached  its  maximum  heat.  The  gas 
from  the  dust  catcher  is  then  shut  off,  the  chimney  damper  is 
closed,  the  valves  connecting  the  stove  to  the  cold  and  hot  blast 
mains  are  opened,  and  atmospheric  air  is  forced  by  blowers  through 
the  stove  in  a  direction  opposite  to  that  taken  by  the  gases  which 
were  burned  to  heat  the  brickwork.  This  part  of  the  operation  con- 
tinues for  a  half  hour  or  more,  during  which  the  air  is  delivered 
very  hot  to  the  hot  blast  main.  The  operation  is  again  reversed  as 
soon  as  the  brickwork  begins  to  become  appreciably  cooled. 

At  least  two  stoves,  and  usually  four,  are  installed  for  each  blast 
furnace,  so  that  at  least  one  stove  may  be  constantly  in  use  for  each 
part  of  the  reverse  operation  just  described. 

59.  Reverberatory  Furnaces. — Two  types  of  the  reverberatory 
furnace  are  used  in  smelting.  Fig.  9  shows  a  roasting  furnace  in 
which  ores  are  roasted  to  simplify  them  before  they  are  placed  in 
the  melting  furnace  shown  in  Fig.  10.  The  melting  furnace  is 
much  used  for  smelting  copper  and  tin  ores,  for  refining  copper  and 
tin,  and  for  melting  copper  and  brass  in  large  quantities  in  the 
foundry  for  castings. 

Both  furnaces  have  several  similar  parts,  as  follows : 

G.    Grate  for  fuel.    D.    Fuel  door. 

A.    Ash  pit, 

W.  Bridge  wall  to  separate  the  fuel  from  the  ore  or  metal  in  the 
furnace. 


GENERAL  OUTLINE  OF  METAL-PRODUCING  PROCESSES        49 

B.  Furnace  arch,  which  reflects  heat  down  upon  the  furnace 
charge. 

F.    Hearth,  on  which  the  charge  rests. 

C.  Chimney  opening,  controlled  by  a  damper. 

These  furnace  roofs  are  arched  from  side  to  side,  and  the  sides 
are  "braced  by  iron  plates  connected  with  long  rods  over  and  under 
the  brickwork  of  the  furnace.  The  melting  furnace  must  generate 


FIG.  9. — Reverberatory  Furnace  for  Roasting. 


FIG.  10. — Reverberatory  Furnace  for  Melting. 

a  more  intense  heat  than  the  other,  hence  its  fire  box  is  larger. 
These  furnaces  have  no  air  blast,  and  their  draft  is  produced  by  a 
tall  chimney.  The  fuel  is  usually  oil,  gas,  or  soft  coal  which  pro- 
duces a  long  flame. 

The  roasting  furnace  has  a  flat  hearth  over  which  the  ore,  intro- 
duced through  covered  hoppers  H,  is  evenly  spread.  The  hearth  is 
so  shaped  that  every  part  of  it  can  be  reached  by  a  rake  or  rabble 
through  one  of  the  doors  M  (two  on  each  side)  and  when  roasting 
has  reached  the  proper  degree,  a  plate  in  the  hearth  at  the  edge  of 


50  MECHANICAL  PROCESSES 

each  door  is  lifted  and  the  charge  raked  into  the  arched  space  L. 
From  there  it  is  taken  to  the  melting  furnace. 

In  the  regular  process  of  smelting,  the  slope  of  the  bottom  leads 
the  metal  to  the  breast  K  (Fig.  10)  from  which  it  is  tapped.  This 
opening  is  stopped  with  a  clay  plug  which  is  dug  out  by  a  pointed 
iron  bar  when  the  metal  is  to  be  drawn  off.  The  slag  is  removed 
through  an  opening  at  the  back  of  the  furnace,  higher  than  the 
breast  opening. 

After  charging  the  furnace  with  ore  and  flux,  the  door  H  is 
plastered  around  the  edges  with  clay  to  exclude  air.  The  progress 
of  the  operation  is  watched  and  any  stirring  needed  is  done  through 
the  small  covered  opening  P. 

Unlike  the  blast  furnace,  the  melting  reverberatory  furnace  can 
be  placed  in  operation  and  cooled  down  in  a  short  time.  Usually 
only  a  single  charge  is  smelted  and  drawn  off,  after  which  the  fur- 
nace is  opened,  recharged,  and  again  put  in  operation  without  much 
lessening  of  temperature.  Feeding  hoppers  may  be  placed  on  top 
and  the  furnace  made  to  operate  continuously. 

60.  Atmosphere    of    Keverberatory   Furnaces. — These    furnaces 
may  be  so  fired  and  the  air  supply  to  the  fire  so  regulated  as  to  make 
the  furnace  action  oxidizing  or  reducing.     Oxidation  demands  (1) 
an  excess  of  air  beyond  that  needed  for  complete  oxidation  of  every 
combustible  part  of  the  fuel  and  (2)  that  the  excess  air  be  at  the 
required  heat  to  combine  with  (burn)  the  material  to  be  oxidized. 

Reduction  demands  ( 1 )  that  the  supply  of  air  be  deficient  for  the 
complete  burning  of  the  fuel  and  (2)  that  the  unburned  gases  from 
the  fuel  be  kept  at  or  above  their  igniting  temperature,  in  which 
case  they  will  extract  oxygen  from  oxides  in  the  charge  having  a 
less  affinity  for  oxygen.  An  oxidizing  atmosphere  necessitates  a 
thin  fire  and  a  full  supply  of  air  over  and  under  the  fuel,  while  a 
reducing  atmosphere  necessitates  a  thick  fire  with  small  air  supply, 
particularly  above  the  fuel.  In  both  operations  it  is  imperative  that 
the  fire  shall  burn  vigorously  enough  to  maintain  the  degree  of  heat 
required.  Eeverberatory  furnaces  are  not  economical  in  fuel. 

61.  Refractory   Materials. — An    important   feature   demanding 
particular  attention  in  all  furnaces  is  the  interior  lining,  because  of 
the  intense  heat  and  the  chemical  action  to  which  furnace  linings 
are  subjected.    A  lining  must  (1)  resist  oxidation  and  reduction, 


GENERAL  OUTLINE  OF  METAL-PRODUCING  PROCESSES        51 

(2)  must  not  melt  nor  disintegrate  from  heat,  (3)  must  reasonably 
stand  the  mechanical  wear  of  the  furnace  charge,  and  (4)  must  not, 
unless  so  intended,  enter  into  chemical  combination  with  the  fur- 
nace charge.  Crucibles,  in  which  metal  is  melted,  the  linings  of 
ladles  for  receiving  and  pouring  molten  metals,  and  the  linings  of 
all  classes  of  heating  furnaces  must  fulfill  substantially  the  same 
requirements. 

The  refractory  materials  commonty  used  in  all  branches  of  smelt- 
ing, refining  and  melting  of  metals,  including  the  processes  of  steel 
making,  and  in  heating  furnaces,  are 

(1)  Silica  (common  sand),  Si02. 

(2)  Silicate  of  Aluminum  (clay),  Al2032Si022H20. 

(3)  Magnesite  (magnesia),  MgO. 

(4)  Chromite  (chromium  oxide),  Cr203FeO. 

(5)  Dolomite  (magnesian  limestone). 

(6)  Bauxite  (alumina),  A1203. 

All  of  these  substances  are  more  or  less  impure  as  found  in  na- 
ture, containing  iron  oxide,  sand  and  clay,  and  in  some  cases,  soda, 
potash,  and  organic  matter.  Practice  has  established  the  limit  of 
impurities  not  detrimental  to  the  uses  of  these  materials  for  specific 
purposes. 

Silica  and  clay  are  closely  associated  in  use  as  refractory  mate- 
rials. They  are  used  far  more  than  the  other  substances  named, 
and  are  adapted  for  use  in  many  kinds  of  furnaces.  A  mixture  of 
the  two  materials  is  known  as  fire  day,  and  different  proportions  of 
the  mixtures  are  employed  in  different  furnaces,  according  to  re- 
sults obtained  by  experience.  Silica  resists  the  action  of  heat  and 
alumina  resists  the  action  of  metallic  oxides.  Silica  is  not  plastic 
when  wet  and  must  be  mixed  with  enough  clay  to  make  the  grains 
stick  together.  Ganister  is  a  natural  rock  composed  of  silica  and 
clay  in  the  proportion  for  making  high-grade  fire  brick. 

Silica  is  an  "  acid  "  material  and  cannot  be  used  for  bottoms  of 
furnaces  for  basic  steel  making,  and  for  linings  of  other  furnace 
bottoms  requiring  basic  material.  For  these  uses,  magnesite  and 
chromite  are  used  in  brick  form,  and  dolomite  is  used  for  patching, 
but  it  is  more  or  less  objectionable  because  of  its  lime  content,  an 
excessive  amount  of  which  causes  disintegration  at  high  tempera- 
tures. Chromite  is  a  neutral  material,  that  is,  it  is  neither  acid, 


52  MECHANICAL  PROCESSES 

basic,  oxidizing  nor  reducing  in  its  chemical  action,  and  is  unex- 
celled for  use  where  a  material  is  needed  to  resist  high  heat  and 
chemical  action. 

Bauxite  is  exceedingly  refractory  and  is  neutral,  but  has  very 
limited  use  because  it  is  subject  to  excessive  shrinkage  and  loses 
plasticity  when  highly  heated. 

Refractory  materials  are  much  used  in  the  form  of  fire  bricks. 
There  are  many  standard  commercial  shapes  of  fire  bricks,  and 
many  grades  also,  according  to  the  purity  of  materials,  skill  in 
shaping  and  care  in  burning.  The  selected  materials  are  thoroughly 
calcined,  ground,  well  mixed  in  correct  proportions  with  water, 
moulded  to  shape,  dried  in  the  open  air,  and  slowly  burned  in  a 
kiln  which  must  be  heated  to  a  white  heat  and  gradually  allowed 
to  cool.  About  1  per  cent  of  lime  in  silica  bricks  is  necessary  to 
fuse  the  particles  together  when  burned.  All  bricks  should  be  true 
to  shape,  and  their  surfaces  must  allow  them  to  lie  in  close  contact 
when  placed  for  use.  Each  grade  of  bricks  must  be  laid  in  a  cement 
or  mortar  of  like  material  ground  fine.  This  cement  fills  spaces 
between  the  bricks,  uniting  the  whole  in  a  compact  mass. 

A  good  fire  brick  when  broken  should  not  show  a  crumbly  mass  of 
ingredients,  with  large  grains  of  material  loose  and  ready  to  fall 
out,  but  the  mass  should  be  dense,  strong  and  thoroughly  fused 
together. 

62.  Sources  of  Copper. — The  greater  part  of  the  world's  supply  of 
copper  is  produced  by  smelting  the  sulphide  ores.    A  very  extensive 
source  of  supply  of  native  copper  is  the  Lake  Superior  deposit. 
Only  a  small  supply  of  copper  comes  from  oxides,  carbonates  and 
low-grade  ores. 

The  sulphides  and  other  ores,  including  those  containing  as  little 
as  5  or  6%  of  copper,  are  smelted;  native  copper  is  melted  down 
to  separate  it  from  rock  and  other  earthy  substances  it  holds;  and 
very  low-grade  ores  are  leached  by  the  wet  process. 

63.  Producing  Copper  from  its  Sulphides. — In  the  smelting  proc- 
ess, which  is  preceded  by  roasting  the  ores  to  remove  some  of  the 
sulphur,  large  lump  ores  not  too  complicated  with  gangue  and  other 
metals,  are  smelted  in  the  blast  furnace,  while  the  powdered  ores 
and  those  of  complex  composition  are  smelted  in  the  reverberatory 
furnace. 


GENERAL  OUTLINE  OF  METAL- PRODUCING  PROCESSES        53 

The  process  of  producing  copper  is  not  direct  and  simple,  as  is  the 
case  with  iron,  but  consists  of  a  number  of  treatments  under  sep- 
arate heats,  or  in  separate  furnaces  and  receptacles.  The  object  of 
the  several  steps  of  the  process  is  to  simplify  the  copper  compounds 
into  a  nearly  pure  sulphide  by  removal  of  other  parts  of  the  ore, 
principally  iron  and  an  excess  of  sulphur,  and  then  to  break  up  the 
copper  sulphide  and  remove  its  sulphur  by  oxidation,  leaving  a 
somewhat  impure  metallic  copper  which  is  then  refined. 

Roasting  the  ore  removes  some  of  the  sulphur  and  incidentally 
oxidizes  some  of  the  free  copper  and  iron.  The  roasted  ore  is  then 


FIG.  11. — Copper  Converter. 

melted  in  a  smelting  furnace  to  convert  the  earthy  matter  into  slag 
by  use  of  flux,  as  in  iron  smelting,  and  the  remaining  product  is  a 
nearly  pure  sulphide  of  copper  in  which  some  iron  sulphide  remains. 
This  product,  known  as  " matte "  or  "coarse  metal/'  is  run  in  a 
molten  state  from  the  smelting  furnace  into  a  large  refractory  lined 
vessel  called  a  converter,  and  cold  air  is  blown  through  the  molten 
mass  to  oxidize  the  sulphur  and  the  iron. 

Fig.  11  shows  a  cross-section  of  a  converter.  It  consists  of  a  shell 
fc  of  steel  plates  with  a  lining  dd  of  silica.  The  trunnion  band  aa 
supports  the  converter  and  allows  it  to  be  tilted  about  an  axis  & 
perpendicular  to  the  plane  of  the  page.  The  wind  box  /  extends 


54  MECHANICAL  PROCESSES 

part  way  around  the  bottom.  It  receives  air  through  one  of  the 
trunnions,  which  is  hollow  and  connected  to  a  blower.  The  air  is 
forced  through  several  openings,  as  at  g,  into  the  molten  charge. 
It  combines  with  the  sulphur,  forming  sulphur  dioxide  which  es- 
capes at  h  into  the  open  air.  The  iron  in  the  charge  is  also  oxidized, 
this  oxide  forming  a  slag  with  the  silica  lining  of  the  converter. 
The  oxidation  of  sulphur  and  iron  supplies  heat  which  keeps  the 
charge  molten,  and  the  blow  is  continued  until  the  flame  from  the 
converter  mouth  shows  that  these  are  about  burned  out  and  that 
copper  is  beginning  to  burn.  The  converter  is  then  tilted  in  the 
direction  of  the  arrow  to  pour  the  charge  into  a  ladle.  The  product 
thus  obtained  is  copper  about  98  or  99%  pure,  known  as  "blister 
copper,"  because  of  the  blisters  on  its  surfa.ce  due  to  expelling  sul- 
phur dioxide  as  the  metal  cools. 

The  last  stage  is  the  refining  of  blister  copper  either  by  the  poling 
process  or  by  electrolysis.  The  object  is  the  same  in  both  cases,  viz., 
to  remove  the  remaining  sulphur,  iron,  copper  oxide,  antimony, 
arsenic  and  other  less  frequent  impurities.  The  purpose  for  which 
the  copper  is  to  be  used  and  the  kind  of  impurity  it  contains  deter- 
mine the  degree  of  refining  necessary,  though  not  over  .5%  of  com- 
bined impurities  should  remain  in  any  grade  of  refined  copper. 

64.  The  Poling  Process. — This  consists  of  melting  blister  copper 
in  a  reverberatory  furnace  and  stirring  it  to  bring  about  the  chemical 
action  necessary  to  remove  the  remaining  impurities. 

A  charge  is  melted  under  the  heat  of  an  oxidizing  flame  and  its 
surface  is  agitated  by  means  of  a  heavy  hoe,  or  rabble,  to  bring  the 
impurities  in  reach  of  the  flame.  This  is  called  "flapping." 
Samples  of  metal  dipped  from  the  furnace  during  this  process  en- 
able the  rabbler  to  judge  its  progress. 

When  the  oxidizable  impurities  are  burned  out,  the  next  step  is 
to  remove  the  copper  oxide.  The  slag  produced  by  flapping  is  drawn 
off,  the  furnace  flame  is  changed  from  oxidizing  to  reducing,  and 
the  metal  is  covered  with  charcoal.  Wood  poles  are  then  used  to 
stir  the  charge.  These  supply  carbon  which  assists  the  charcoal 
to  reduce  the  oxide,  forming  C02  which  escapes  up  the  chimney. 
Green  wood  is  best,  as  its  moisture  boils  out  and  helps  agitate  the 
molten  metal  to  bring  carbon  and  copper  oxide  in  mutual  contact. 


GENERAL  OUTLINE  OF  METAL-PRODUCING  PROCESSES        55 

When  the  oxide  is  removed,  the  copper  is  tapped  from  the  furnace 
into  a  large  ladle  and  is  poured  into  moulds  made  of  copper.  The 
molten  metal  is  kept  from  sticking  to  the  moulds  by  a  wash  of  thin 
clay,,  and  the  red-hot  pig  or  slab  of  metal  is  dumped  into  a  trough 
of  water  to  soften  it  for  working. 

Poling  requires  much  skill  and  experience  to  know  when  it  has 
proceeded  far  enough.  Too  much  poling  produces  brittle  copper. 

65.  Electrolytic  Refining  of  Copper. — The  malleability  of  copper 
and  its  efficiency  as  a  conductor  of  electricity  are  greatly  reduced  by 
even  the  slightest  impurities  in  the  metal.    The  electrolytic  process 
of  refining  is  used  because  it  gives  a  higher  grade  of  refined  metal 
from  a  greater  range  of  impure  copper  than  is  the  case  with  the 
poling  process. 

Electrolytic  refining  consists  of  dissolving  plates  of  blister  copper 
by  electrolysis  and  depositing  the  metal  from  solution  upon  a  pre- 
viously prepared  sheet  of  pure  copper.  The  current  gradually  dis- 
solves the  plate  of  blister  copper  and  deposits  the  metal  almost  abso- 
lutely pure  upon  the  other  plate.  The  impurities  from  the  dissolved 
sheet  either  go  into  solution  in  the  liquid  of  the  tank  in  which  the 
process  is  carried  on,  or  fall  to  the  bottom  in  the  slime. 

A  plate  of  copper  thus  prepared  is  too  porous  for  use,  hence  it  is 
melted  and  cast  into  cakes,  ingots  or  wire-bars,  as  may  be  needed. 

66.  Zinc  is  obtained  from  the  sulphide,  or  "blende";  and  to  a 
smaller  extent  from  the  carbonate  and  oxide.     There  are  several 
complex  zinc  ores,  and  some  of  these,  as  the  zinc  and  lead  sulphides, 
are  abundant,  but  so  far  no  method  has  been  found  for  the  profitable 
extraction  of  the  metals. 

The  essential  steps  in  extracting  zinc  are: 

(1)  Changing  the  ore  to  an  oxide,  by  calcining  the  less  stable 
ores  and  roasting  the  sulphides.     Calcining  is  done  in  kilns,  and 
roasting  is  done  in  reverberatory  furnaces. 

(2)  Eeducing  the  oxide.    This  is  done  by  mixing  the  pulverized 
oxide  with  carbon  and  heating  in  clay  retorts.    The  high  heat  neces- 
sary to  accomplish  the  reduction  (1900°  F.)  not  only  liberates  the 
zinc,  but  vaporizes  it,  and  the  vapor  is  condensed  in  suitably  placed 
iron  tubes  which  drain  the  liquid  zinc  into  ladles  from  which  it  is 
poured  into  ingots. 


56  MECHANICAL  PROCESSES 

(3)  Eefining  the  ingots.  They  are  remelted  in  quantities  of 
several  tons  in  a  specially  constructed  reverberatory  furnace.  The 
molten  metal  is  allowed  to  remain  quiet  for  a  few  days,  when  the 
floating  impurities  are  skimmed  off.  Molten  lead  and  iron,,  which 
are  almost  always  present,  sink  to  the  lowest  part  of  the  furnace 
basin  and  are  quietly  tapped  out,  the  lead  running  out  first,  fol- 
lowed by  the  iron,  which  carries  some  zinc  also.  The  remaining 
zinc  is  run  out  and  cast  into  slabs  or  ingots  for  marketing.  These 
are  known  as  "spelter/'  and  should  contain  not  over  1%  of  lead 
and  only  traces  of  iron. 

A  recent  refining  process  for  zinc  consists  of  passing  the  vapor 
from  the  reducing  retorts  through  a  filter  of  coke  kept  hot  enough 
to  prevent  condensation.  This  is  said  to  remove  iron  and  lead  better 
than  by  the  method  of  re-melting. 

67.  Tin  is  produced  from  its  oxide  (Sn02)   known  as  stannite, 
casserite,  or  tin-stone,  which  is  not  so  abundantly  distributed  as  are 
ores  of  many  other  metals.    The  oldest  mines  are  in  England  and 
the  East  Indies,  though  ore  deposits  in  Europe  and  America  are 
now  worked.    The  best  grade  of  commercial  tin  is  said  to  be  from 
Banca,  in  the  East  Indies. 

68.  Lead  is  produced  mainly  from  its  sulphide,  known  as  galena. 
The  smelting  of  this  ore  is  complicated  by  the  presence  of  arsenic, 
copper,  iron,  zinc,  or  silver,  and  like  the  smelting  of  copper  sul- 
phides, the  process  is  one  of  desulphurization.     The  blast  furnace, 
usually  of  rectangular  cross-section,  is  now  generally  used  for  smelt- 
ing lead,  though  if  the  ore  is  rich  in  sulphur,  it  is  first  roasted  in  a 
reverberatory  furnace  to  drive  off  sulphur  and  oxidize  some  of  the 
ore.    A  flux  of  iron  oxide  and  limestone  assist  in  reducing  the  ore, 
and  the  impure  metal  is  drawn  off  through  an  opening  in  the  base 
of  the  furnace  leading  outward  and  upward  from  the  bottom  of  the 
hearth. 

69.  Nickel  is  produced  from  the  arsenide,  known  as  kupfer- 
nickel,  and  to  a  lesser  extent  from  the  sulphide. 

The  smelting  process  is  somewhat  complex  and  is  accomplished 
by  roasting,  reducing  in  presence  of  flux,  and  Bessemerizing.  The 
sulphide  is  then  changed  by  roasting  to  oxide,  which  is  finally  re- 
duced with  charcoal. 


GENERAL  OUTLINE  OF  METAL-PRODUCING  PROCESSES        57 

70.  Aluminum  never  occurs  free  in  nature,  but  no  other  metal 
known,  not  excepting  iron,  occurs  in  such  abundance  in  its  com- 
pounds, nor  is  any  other  metal  so  widely  distributed  over  the  earth. 
Its  combination  with  oxygen,  silicon,  alkalies  and  acids  forms  clay, 
koalin,  emery,  mica,  feldspar  and  many  of  the  precious   stones. 
It  is  obtained  mostly  from  Bauxite,  an  oxide  known  as  alumina,  first 
found  near  Baux,  in  France.     This  is  dissolved  in  a  fused  bath  of 
cryolite  (a  fluoride  of  sodium  and  aluminum)   by  the  heat  of  an 
electric  current.     This  heat  fuses  the  cryolite,  which  in  turn  dis- 
solves the  alumina,  in  which  condition  the  electrolytic  action  of  the 
current  decomposes  the  alumina,  but  does  not  change  the  cryolite. 
The  liberated  metal  sinks  to  the  bottom  of  the  vessel  and  is  siphoned 
off  when  it  accumulates.     The  process  is  continuous  so  long  as 
alumina  is  supplied  and  the  current  is  maintained. 

71.  Electricity  in  Metallurgy. — Electrolytic  action  has  long  been 
applied  to  electro-plating,  and  in  recent  years  to  the  refining  of 
copper.    The  combined  electrolytic  and  heat  actions  of  current  are 
used  in  producing  aluminum,  and  very  recently  the  heat  of  the 
electric  arc  has  been  made  commercially  successful  in  refining  steel 
from  a  lower  quality  to  a  higher  quality. 

The  advantages  of  the  higher  heat  of  the  electric  furnace,  and  its 
easy  control,  make  the  application  of  electric  heat  to  the  smelting 
of  metals  highly  desirable,  at  least  to  the  extent  of  (1)  assisting  the 
fuel  at  the  point  of  ore  fusion,  (2)  of  making  the  extracted  metal 
more  fluid,  and  (3)  of  improving  its  quality  by  producing  a  neutral 
atmosphere  due  to  electric  heating  as  compared  with  the  oxidizing 
atmosphere  of  fuel  heating.  Also,  as  some  impurities  come  from  the 
fuel  used,  the  reduction  in  fuel  reduces  the  per  cent  of  these,  par- 
ticularly so  of  phosphorus. 

Recent  experiments  in  Sweden  have  shown  that  an  improved 
grade  of  iron  can  be  made  in  a  combined  electric  and  fuel  furnace, 
but  as  yet  this  is  not  economical  enough  for  commercial  require- 
ments in  general. 


CHAPTEE  III. 
FUELS. 

72.  Uses. — The  use  of  fuels  of  different  kinds  is  highly  essential 
in  the  various  industries  for  the  producing  and  shaping  of  metals. 
Heat  is  indispensable   (1)   to  bring  about  chemical  action  which 
breaks  up  the  ore  compounds  in  the  smelting  of  metals,   (2)   for 
many  chemical  and  mechanical  operations  as  the  refining  of  metals 
and  the  making  of  wrought  iron  and  steel,  and  (3)  for  softening 
or  melting  metals  to  assist  in  their  shaping  for  definite  uses. 

73.  Combustion. — The  economical  use  of  fuel  requires  that  none 
of  it  should  be  wasted  in  an  unburned  state,  as  is  frequently  the  case 
in  the  escape  of  unburned  gases  up  the  chimney.    Combustion  is  the 
chemical  union  of  an  oxidizable  substance  with  oxygen,  and  when 
this  is  accomplished  rapidly,  as  in  ordinary  burning,  an  intense 
degree  of  heat  is  generated.    Flame  is  caused  by  the  burning  of  gas. 
The  flame  from  solid  or  liquid  fuel  is  caused  by  the  burning  of  gas 
distilled  from  the  fuel.     The  presence  of  fuel  in  many  metal  pro- 
ducing and  metal  shaping  operations  is  objectionable  (though  un- 
avoidable) for  the  following  reasons,  viz. :  in  the  presence  of  high 
heat  (1)   the  oxygen  necessary  for  combustion  consumes  more  or 
less  of  the  metal  or  other  material  subjected  to  the  operation,  and 
(2)   the  substance  of  the  fuel,  and  particularly  the  impurities  in 
the  fuel,  combine  with  a  metal  in  the  process  of  smelting  and  in  sub- 
sequent heating  or  melting  operations  and  impair  its  quality. 

The  essentials  for  burning  fuel  completely,  with  no  visible  smoke 
and  no  waste  of  combustible  substance,  are  (1)  every  particle  of 
combustible  substance  must  be  supplied  with  the  oxygen  necessary 
for  complete  oxidation,  and  (2)  the  fuel  and  the  oxygen  must  be 
hot  enough  to  combine. 

Every  combustible  substance  must  be  heated  up  to  a  definite 
temperature,  called  the  temperature  of  ignition,  before  it  will  burn. 
Each  burnable  substance  has  a  temperature  of  ignition  differing 
more  or  less  from  that  of  other  substances. 

In  the  confined  space  of  a  furnace,  coal  in  small  lumps  or  porous 
coke  present  much  surface  to  combustion  and  therefore  burn  rapidly, 
but  if  coal  is  too  fine,  it  masses  together  and  leaves  too  little  pass- 
age for  air. 


FUELS 


59 


74.  Components  of  Fuels, — The  heat-producing  elements,  i.  e.f  the 
combustible  substances,  of  all  fuels,  whether  solid,  liquid,  or  gase- 
ous, are  carbon  and  hydrogen.     Many  fuels,  particularly  coal,  con- 
tain free  sulphur,  which  is  always  more  or  less  objectionable,  some- 
times seriously  so,  and  although  sulphur  produces  heat  when  burned, 
its  quantity  is  too  small  to  be  considered  in  summing  up  the  heat 
value  of  a  fuel. 

Almost  all  fuels  contain  ash,  water  and  other  matter  which  will 
not  burn,  and  these  determine  largely  the  practical  and  commercial 
values  of  all  fuels.  These  are  of  negative  value  in  fuel,  as  they 
absorb  and  carry  away  heat  when  the  fuel  is  burned. 

The  heating  or  calorific  value  of  a  fuel  is  usually  expressed  in 
British  Thermal  Units.  One  B.  T.  U.  is  that  quantity  of  heat 
necessary  to  raise  the  temperature  of  one  pound  of  pure  water 
through  1°  F.,  at  or  near  39.1°  F.,  its  point  of  greatest  density. 
The  heat  value  of  a  fuel  is  stated  as  that  quantity  of  B.  T.  U.'s 
which  one  pound  of  the  fuel  will  evolve  when  burned. 

In  commercial  practice,  fuel  is  usually  sold  by  weight,  but  the 
heat  value  of  a  fuel  is  only  crudely  expressed  by  its  weight.  The 
value  of  a  fuel  for  practical  purposes  is  far  better  expressed  by  the 
number  of  heat  units  which  a  given  weight  of  it  will  supply  when 
burned.  The  desirability  of  coal  is  also  determined  by  the  sulphur 
it  contains,  and  by  the  character  and  quantity  of  the  ash  it  makes,  as 
some  coals  produce  a  sticky  clinker  hard  to  remove  from  the  grate 
bars. 

75.  Classes  of  Fuel. — The  following  classification  includes  all 
fuels  in  general  use  in  the  arts  and  industries.    Some  of  these  have 
but  limited  and  special  uses  in  the  metal  industries. 


(1)   Solid  Fuels. 

(a)  Natural  Fuels. 

Wood. 

Peat. 

Coal. 

(b)  Prepared  Fuels. 

Charcoal. 
Coke. 

Powdered  Coal. 
Briquettes. 


(2)  Liquid  Fuels. 

(a)  Natural  Fuels. 

Mineral  Oils. 

(b)  Prepared  Fuels. 

Refined  Mineral  Oils. 
Alcohols. 

(3)  Gaseous  Fuels. 

(a)  Natural  Gas. 

(b)  Prepared  Gases. 

Producer  Gas. 
Water  Gas. 
Illuminating  Gas. 


60  MECHANICAL  PROCESSES 

76.  Wood  and  Charcoal. — Wood  is  less  and  less  used  as  fuel  be- 
cause of  its  increasing  scarcity  and  because  coal  is  abundant  and 
easily  handled.     Charcoal,  made  from  wood,  is  now  used  only  for 
special  purposes  because  of  its  high  cost.     Charcoal  is  prepared  by 
heating  wood  to  a  high  heat  and  thereby  distilling  off  nearly  all 
water  and  volatile  gases,  leaving  only  carbon  and  non-combustible 
mineral  salts.    The  heating  must  be  done  under  a  covering  which 
will  exclude  air. 

In  later  processes,  charcoal  is  produced  in  kilns,  or  in  closed 
retorts  in  which  wood  is  distilled  for  pyroligneous  acid  and  wood  al- 
cohol, and  charcoal  is  a  by-product. 

77.  Coal  is  the  most  extensively  used  of  all  fuels.    The  different 
varieties  of  coal,  with  many  different  names,  merge  one  into  an- 
other, and  the  fundamental  distinction  between  the  several  varieties 
is  the  difference  in  the  amount  of  carbon  contained.     The  several 
grades  or  qualities  of  each  variety  are  due  to  the  per  cent  of  sul- 
phur,   ash    and    water    contained.      Coal    usually    contains    some 
phosphorus. 

A  good  practical  classification  of  the  varieties  of  coal  is : 

(1)  Bituminous  or  soft  coal. 

(a)  Non-caking  varieties,  long  flame  and  gas  coals,  40  to 

70%  fixed  carbon. 

(b)  Caking,  or  coking  varieties.    Short  flame  coals,  55  to 

80%  fixed  carbon. 

(2)  Anthracite  or  hard  coal,  80  to  95%  fixed  carbon. 

There  are  many  grades  of  each  kind,  beginning  with  lignite,  a 
brown  soft  coal  low  in  carbon,  and  ranging  gradually  through  the 
bituminous  to  the  anthracite  coals  which  are  very  rich  in  carbon  and 
contain  very  little  hydrogen.  The  flame  from  coal  is  due  to  the 
gases  which  are  distilled  off  by  the  heat  of  the  fire  and  burn  after 
they  are  thus  liberated.  Fixed  carbon  is  the  solid  carbon  in  coal 
as  distinguished  from  the  gaseous  carbon,  which  is  that  combined 
with  hydrogen. 

Bituminous  coals  constitute  most  of  the  world's  supply.  They 
are  fragile,  and  burn  with  more  or  less  flame  and  smoke.  From 
this  variety  of  coal,  coal  gas  and  coke  are  made.  Cannel  coal  is  a 
variety  of  bituminous  coal. 


FUELS 


61 


Anthracite  coal  has  a  lustrous  black  color,  is  hard,  and  does  not 
readily  pulverize  in  handling,  hence  is  comparatively  free  from  dust. 
The  best  varieties  give  off  very  little  gas,  hence  they  burn  as  in- 
candescent coals  with  very  short  flame.  The  purer  varieties  are  used 
in  smelting  furnaces  occasionally,  and  more  frequently  to  melt 
metal  in  crucibles. 

78.  Coke  is  a  product  of  bituminous  coal,  bearing  the  same  rela- 
tion to  coal  which  charcoal  bears  to  wood.     The  better  varieties, 
made  from  the  softer  bituminous  coals,  and  used  almost  entirely 
in  the  blast  furnace  and  for  melting  metals  in  the  foundry,  are 
primary  products,  while  the  poorer  varieties  are  b}^-products  from 
the  manufacture  of  coal  gas.    A  good  grade  of  coke  must  be  porous, 
yet  not  fragile,  for  it  must  not  be  crushed  by  the  weight  of  the 
charge  in  a  furnace;  and  it  must  contain  little  sulphur  or  ash, 
which  requires  that  it  be  made  from  a  good  grade  of  coal. 

79.  Coke  Making. — Coke  is  made,  by  subjecting  coking  coal  to  a 
high  heat  for  about  four  days,  without  free  access  of  air.     This 
process  drives  off  water  and  the  hydrocarbon  gases,  leaving  the  free 


FIG.  12. — Coke  Oven. 

carbon  and  ash.  Coal  should  be  selected  which  contains  little  sul- 
phur, as  all  of  this  is  not  driven  off  in  coking.  Fig.  12  shows  a 
simple  type  of  coke  oven  which  is  still  used,  though  more  elaborate 
and  more  economical  ovens  are  displacing  it.  This  type,  known 
as  the  bee-hive  oven,  is  shown  here  because  of  its  simplicity.  This 
form  of  oven  is  low  in  cost  to  build  and  to  maintain,  and  is  a  good 
coke  producer.  A  number  of  ovens  are  built  together  to  economize 
space  and  heat.  This  oven  is  a  chamber  formed  of  brickwork,  lined 
5 


62  MECHANICAL  PROCESSES 

with  fire  brick,  and  provided  with  an  opening  a  in  the  top  and  a 
door  at  the  side.  Two  styles  of  doors  are  here  shown  in  two  of  the 
ovens.  Doors  are  lined  inside  with  fire  brick,  and  are  provided  with 
dampers.  The  lower  part  of  the  chamber  is  circular,  about  10  ft. 
in  diameter,  and  is  surmounted  by  a  hemispherical  dome. 

A  charge  of  coke  having  been  removed  through  the  door,  the  oven 
is  left  at  a  dull  red  heat.  The  door  is  closed  and  luted  with  elay, 
except  that  a  few  peep  holes  are  left  for  watching  the  process  and 
for  admitting  air  for  combustion.  A  charge  of  several  tons  of  coal 
is  dumped  in  at  the  top  opening  from  a  car  which  moves  along  rails 
laid  over  the  furnaces.  The  furnace  heat  soon  begins  to  distil  off 
the  gaseous  parts  of  the  coal,  which  are  ignited  by  the  admission 
of  air  at  the  dampers,  and  this  combustion  supplies  heat  which  con- 
tinues the  coking  process.  It  requires  several  hours  for  the  charge 
to  get  thoroughly  hot  throughout,  and  the  distillation  of  gases 
gradually  extends  into  the  mass,  and  when  a  maximum  amount  of 
gas  is  being  evolved,  the  furnace  lining  and  charge  are  at  a  red  heat. 
After  about  thirty  hours  the  evolution  of  gas  begins  to  decrease, 
and  a  little  air  continues  to  be  admitted  until  all  flame  ceases,  when 
air  is  shut  off  entirely.  The  furnace  is  now  nearly  white  hot,  and 
combustion  is  stopped  entirely,  for  the  charge  must  cool  down 
before  it  can  be  withdrawn.  After  about  twelve  hours  the  charge 
has  cooled  to  a  degree  which  will  allow  a  limited  amount  of  water 
to  be  introduced  from  a  hose  for  quicker  cooling,  and  after  a  short 
time  the  door  can  be  opened  wide  and  the  charge  raked  out  into 
iron  barrows. 

In  this  type  of  furnace  the  products  of  distillation  escape  par- 
tially burned  through  the  top  opening,  and  may  be  completely 
burned  elsewhere,  as  they  are  rich  in  combustible  gases.  It  is 
sought  in  coking  to  heat  the  mass  of  coal  from  above  by  burning 
some  of  the  distilled  gases  before  they  escape  from  the  oven,  but  the 
burning  of  some  of  the  solid  carbon  is  unavoidable,  hence  this  fur- 
nace is  not  so  economical  as  some  of  the  later  types. 

80.  Powdered  Coal  has  a  limited  use  in  metal  heating  furnaces. 
It  is  ground  to  a  fine  dust  by  revolving  it  in  a  steel  drum  with  hard 
pebbles.  It  is  then  conveyed  through  tightly  made  sheet  iron  tubes 
to  the  furnaces,  and  is  blown  into  the  flame  of  the  furnace  by  air 
pressure  through  a  specially  constructed  burner  for  regulating  both 
air  and  fuel. 


FUELS  63 

81.  Screenings.     Briquettes. — In  handling  coal  at  the  mine,  a 
considerable  quantity  becomes  pulverized.    In  this  form  it  is  known 
commercially  as  screenings.     This  is  now  used  in  mechanical  stokers 
fitted  to  steam  boilers,  and  some  of  it  is  made  into  briquettes  by 
mixing  it  with  tar  or  crude  oil  and  pressing  it  into  cakes  by  a  machine 
for  that  purpose.    Some  grades  of  screenings  must  be  washed  to  re- 
move mineral  matter. 

82.  Liquid  Fuels. — The  only  practicable  cheap  liquid  fuel  is  min- 
eral oil,  better  known  as  crude  petroleum,  though  this  is  confined 
to  too  few  localities  for  general  displacement  of  coal,  but  in  those 
localities  is  usually  cheaper  and  more  desirable  than  coal.    It  comes 
from  oil  wells  drilled  usually  deep  into  the  earth.     When  taken 
from  the  earth,  this  oil  is  refined  before  it  can  be  safely  used  for 
fuel.     This  consists  of  subjecting  it  to  two  stages  of  distillation 
which  causes  it  to  give  off  in  turn  highly  inflammable  gases,  gaso- 
lene, benzine,  and  naphtha;  then  kerosene,  and  gas-enriching  oils, 
leaving  a  dark-colored  viscous  liquid  residue  which  is  used  as  fuel. 
Fuel  oil  must  be  strained  and  frequently  is  heated  just  before  it  is 
burned  to  increase  its  fluidity  and  prevent  clogging  the  burners.    It 
is  sprayed  by  pressure  into  the  furnace. 

While  all  mineral  oils  consist  of  the  same  elements,  carbon  and 
hydrogen,  the  oils  from  different  localities  vary  widely  in  the  rela- 
tive amounts  of  gasolene,  kerosene,  lubricating  oil,  and  the  more 
dense  constituents  forming  the  residue,  due  to  the  fact  that  carbon 
and  hydrogen  have  a  great  variety  of  chemical  combinations,  and 
each  of  these  combinations,  or  compounds,  differs  in  volatility  from 
the  others.  This  accounts  for  the  fact  that  some  mineral  oils  have 
a  large  proportion  of  volatile  oils  and  only  a  small  amount  of 
residue,  while  others  have  a  large  proportion  of  residue  and  need 
but  little  distillation  to  prepare  them  for  fuel.  The  residue  of 
mineral  oils  includes  the  heavier  lubricating  oils,  vaseline,  paraffin, 
and  mineral  pitch  better  known  as  asphalt  or  bitumen.  Mineral 
oils  contain  more  or  less  earthy  impurities,  including  sulphur.  It 
is  not  known  from  what  sources  mineral  oil  was  produced  in  its 
natural  deposits. 

Of  the  refined  oils,  gasolene  is  much  used  as  motor  fuel,  and 
kerosene  has  very  limited  use  as  an  industrial  fuel. 

Alcohols   are  produced   from   fermentation   and   distillation   of 


64  MECHANICAL  PROCESSES 

vegetable  matter  and  make  excellent  fuels,  but  they  are  little  used 
at  present  except  in  small  quantity  for  special  needs.  They  are 
considered  superior  to  petroleum  fuels  for  motors,  but  their  pro- 
duction and  development  for  this  use  is  limited  because  of  the  ex- 
tensive use  gained  by  gasoline  while  it  was  very  cheap. 

83.  Gas  Fuels. — The  great  convenience  of  natural  and  producer 
gas  as  fuel  in  reverberatory,  steel-making,  and  metal-heating  fur- 
naces has  caused  extensive  use  of  gas  fuel  in  all  metal  industries. 

For  furnace  use  a  more  concentrated  and  more  intense  heat  can 
be  obtained  from  gas  than  from  coal,  as  a  less  volume  of  air  enters 
the  furnace  with  the  gas,  thus  necessitating  the  heating  of  less 
inert  nitrogen  which  enters  with  the  air.  The  heat  from  gas  can  be 
regulated  and  directed  better  than  that  from  coal,  and  gas  leaves 
no  ash  nor  clinker. 

84.  Natural  Gas,  like  mineral  oil,  is  obtained  from  cavities  in 
which  it  is  confined  in  the  earth.    It  is  abundant  in  a  few  localities 
only,  but  the  great  desirability  of  gas  has  given  rise  to  the  artificial 
production  of  fuel  gas  from  coal,  and  to  a  less  degree  from  oil. 
Natural  gas  is  composed  of  about  93%  CH4,  with  very  little  free 
hydrogen,  CO,  and  nitrogen. 

85.  Producer  Gas  is  made  as  follows,  referring  to  the  gas  pro- 
ducer in  Fig.  13.     A  shell  of  steel  plates,  lined  with  fire-bricks, 
rests  on  a  cast-iron  ring  A,  which  in  turn  is  supported  by  lugs  rest- 
ing on  the  edge  of  a  basin  B.    This  basin,  which  is  a  depression  in 
the  concrete  floor,  is  kept  filled  with  water.     The  interior  of  the 
producer  contains  fuel  in  various  stages  of  burning,  varying  from 
water-soaked  ashes  in  the  basin  at  the  bottom  to  a  continuously  sup- 
plied layer  of  fresh  fuel  at  the  top. 

By  means  of  a  central  tuyere  with  a  mushroom  head  G,  steam 
from  the  pipe  and  nozzle  marked  C,  and  air  drawn  through  the 
damper  D,  are  blown  into  and  distributed  through  the  fuel,  en- 
tering the  hot  ashes  at  G,  and  rising  through  the  zone  of  in- 
candescent fuel.  When  the  air  and  vapor  become  sufficiently  heated, 
the  oxygen  of  the  air  combines  with  the  carbon  of  the  fuel.  The 
tendency  of  this  combustion  is  to  form  C02,  but  the  relatively  small 
quantity  of  oxygen  carried  in  by  the  air  in  presence  of  a  large 
amount  of  incandescent  carbon  soon  reduces  the  C02  to  CO.  The 
heat  produced  by  combustion  is  intense  enough  to  decompose  the 


FUELS 


65 


water  vapor,  the  oxygen  combining  with  the  carbon  of  the  fuel  and 
the  hydrogen  rising  uncombined.  The  gases  resulting  from  this 
partial  combustion  of  fuel  and  the  hydrogen  resulting  from  the 
decomposing  of  steam  rise  into  the  space  above  the  fuel  and  pass 
away  through  the  outlet  K  into  "  scrubbers  "  or  cleaning  compart- 
ments, thence  into  the  storage  tanks  ready  for  use. 


mmm^zm^M^^&^m^i^. 

FIG.  13. — Gas  Producer. 

The  central  opening  at  the  top  is  the  seating  for  an  automatic 
feeder  (not  shown  in  the  sketch)  regulated  to  drop  fuel  into  the 
producer  continuously  at  the  rate  needed.  Fig.  14  shows  a  row  of 
these  feeders,  surmounted  by  coal  hoppers,  along  a  working  floor 
over  the  producers.  The  brick-work  forming  the  body  of  the  fur- 
nace, as  shown  in  Fig.  13,  is  closed  at  the  top  by  a  cast-iron  pan  P, 
which  holds  water  for  keeping  the  top  cool.  This  water  is  received 


66 


MECHANICAL  PROCESSES 


from  a  small  pipe  and  flows  from  the  pan  into  the  ash  basin 
through  a  small  pipe  R  in  the  quantity  needed  to  keep  the  basin  B 
about  full.  It  serves  also  as  a  water  seal  both  in  pan  and  basin  to 
prevent  the  escape  of  gas  from  the  producer.  The  fuel  is  poked 
through  the  holes  //  on  the  side  and  through  the  water-sealed  holes 
M  on  top  if  it  becomes  clogged.  The  small  covers  for  the  water- 


FIG.  14. — Automatic  Feeders  for  Gas  Producers. 

sealed  holes  on  the  top  are  shown  at  the  floor  level  in  Fig.  14.    Ashes 
are  removed  from  the  basin  at  the  bottom  of  the  producer. 

The  gas  product  passing  out  at  K  consists  essentially  of  (1)  CO, 
from  partial  combustion  of  the  fuel,  (2)  hydrogen  from  the  decom- 
posed steam,  (3)  and  a  small  quantity  of  hydrocarbon  gas  distilled 
from  the  coal  as  it  heats  up  before  beginning  to  burn ;  these  are  the 
combustible  gases  and  should  be  about  50%  of  the  whole  volume  of 
gas  produced  for  maximum  efficiency  of  a  producer.  The  remain- 


FUELS  67 

der  of  the  mixture  consists  of  (4)  a  slight  amount  of  C02  from 
complete  burning  of  the  fuel,  and  (5)  considerable  nitrogen  un- 
avoidably entering  as  a  constituent  of  air. 

The  relative  amounts  of  air  and  steam  blown  in  must  be  care- 
fully regulated.  With  no  steam,  the  combustion  would  need  much 
more  air,  resulting  in  larger  proportions  of  nitrogen  and  C02,,  as 
well  as  in  too  intense  a  heat  in  the  producer.  Steam  is  advanta- 
geous because  it  (1)  displaces  nitrogen;  (2)  absorbs  heat  in  its  de- 
composition, thereby  keeping  down  the  temperature  of  the  pro- 
ducer; (3)  supplies  oxygen  for  combustion,  and  (4)  hydrogen  for 
enriching  the  gas  product.  Too  much  steam  checks  combustion  by 
displacing  air  and  by  lowering  the  temperature  of  the  furnace  be- 
low that  required  for  burning  the  fuel. 

Producer  fuel  for  metallurgical  work  usually  consists  of  the  ordi- 
nary grades  of  bituminous  coal,  including  lignite.  Usually  the 
cheapest  grade  of  coal  in  the  locality  where  the  producer  is  installed 
is  suitable  provided  (1)  it  does  not  contain  an  excessive  amount  of 
sulphur  nor  (2)  a  large  per  cent  of  ash  which  forms  pasty  clinkers. 
The  richest  gas  is  made  from  gas  coals  because  of  the  volatile  hy- 
drocarbons they  give  to  the  producer  product.  The  fuel  for  a  pro- 
ducer should  be  in  small  lumps,  because  coal  which  is  wholly 
"  slack  "  or  very  fine  will  resist  the  passage  of  air  and  steam.  There 
are  several  varieties  of  gas  producers  but  all  embody  the  same 
principle. 

86.  Water  Gas  is  produced  by  forcing  steam  through  a  network 
of  very  hot  fire  bricks,  on  the  principle  of  the  blast  stove,  and  im- 
mediately, while  at  a  high  temperature,  through  a  bed  of  incan- 
descent fuel.     The  hot  fuel  decomposes  the  steam,  consuming  the 
oxygen,  liberating  hydrogen  and  giving  off  CO.     In  this  way  no 
nitrogen  is  introduced.     The  blowing  of  steam  through  the  fire  is 
intermittent  as  it  soon  cools  the  fire  and  must  be  shut  off  to  allow 
the  fire  to  regain  heat  by  ordinary  combustion.    Water  gas  produces 
a  more  intense  heat  than  does  producer  gas,  but  is  used  only  for 
special  needs  as  its  cost  is  greater  than  that  of  producer  gas. 

87.  Illuminating  Gas  is  made  in  closed  retorts  from  coals  rich  in 
gas,  and  is  too  expensive  for  extensive  use  as  fuel  in  mechanical 
industries. 


CHAPTEK  IV. 
IRON  AND  STEEL. 

0 

I.  Iron  Ores  and  Their  Reduction.    Pig  Iron. 

88.  Iron  Ores. — These  ores  are  very  widely  distributed  and  very 
abundant  in  nature,  but  many  deposits  cannot  be  worked  profitably. 
According  to  chemical  composition,  ores  available  for  smelting  may 
be  classified  as  follows: 

I.  Magnetic  Iron  Ores,  or  Magnetite  (Fe304). 
II.  Ferric  Oxides  or  Hematites  (Fe203). 

III.  Ferrous  Carbonate  or  Spathic  Ores  (FeC03). 

IV.  Iron  Pyrites   (FeS2,  iron  sulphide  or  fools'  gold)   is  a  very 

abundant  ore,  but  cannot  be  cheaply  smelted  because  of  the 
difficulty  of  eliminating  the  sulphur.  However  when  the 
sulphur  from  this  ore  is  extracted  in  the  manufacture  of 
sulphuric  acid,  the  remaining  product  is  profitably  smelted, 
though  the  iron  obtained  by  this  means  is  but  a  very  small 
per  cent  of  that  smelted. 

The  magnetic  ores,  the.  most  valuable  of  all  iron  ores,  are  black, 
very  dense,  not  so  widely  distributed  as  the  other  ores,  have  mag- 
netic properties  and  contain  about  72%  of  iron  when  pure.  The 
largest  known  deposits  are  in  the  Lake  Superior  region  of  the 
United  States. 

The  hematites  are  usually  red  or  brown  in  color,  according  to  the 
gangue,  are  widely  distributed,  and  usually  free  from  excessive 
sulphur  and  phosphorus.  They  are  employed  more  in  smelting 
than  are  other  ores  because  of  their  abundance. 

89.  Preliminary  Preparation  of  Iron  Ores. — Upon  taking  iron 
ore  from  the  mine,  which  is  usually  a  simple  process  of  excavating 
after  surface  earth  is  removed,  it  is  desirable  to  remove  the  gangue, 
if  this  exists  in  large  quantity,  to  avoid  the  labor  and  expense  of 
its  further  handling.    Magnetic  ore  may  be  lifted  away  from  gangue 
by  electro-magnets,   a  process  known   as   magnetic   concentration. 
Other  methods  of  removing  gangue  have  been  mentioned. 


IRON  AND  STEEL 


69 


90.  Calcination. — The  main  results  of  calcination,  and  the  conse- 
quent advantages  in  smelting  are,  for  iron  ores : 

(1)  Driving  off  water  and  thus  avoiding  interference  with  the 
regularity  of  the  smelter  fire. 

(2)  Elimination  of   C02   and   a  consequent  saving  of  fuel  in 
smelting  as  the  C02  takes  up  much  carbon  from  the  fuel  in  the 
upper  part  of  the  blast  furnace.    This  changes  the  carbonate  ores  to 
oxides. 


FIG.  15. — Bridge  crane  for  handling  ore.  The  unloading  hoists  on  the 
left  take  ore  from  vessels  lying  under  them,  and  pass  it  to  the  bridge 
crane  in  transfer  cars.  This  crane  carries  it  to  its  proper  pile,  accord- 
ing to  composition,  and  also  carries  ore  to  the  charging  cars  of  the 
furnaces  on  the  right. 

(3)  Elimination  of  sulphur  in  some  ores,  thus  preventing  its 
combination  with  the  metal  as  it  melts  and  runs  down  to  the  hearth 
of  the  furnace. 

There  is  no  advantage  in  calcining  the  magnetites  and  red  hema- 
tites unless  they  contain  pyrites.  Ore  deposits  of  the  world  which 
can  be  sent  direct  to  the  smelter  without  sorting  or  calcination  are 
yet  fairly  abundant. 

Fig.  15  shows  the  ore  yard  of  a  large  smelting  plant  where  ore 
is  received  for  smelting. 


70  MECHANICAL  PEOCESSES 

91.  Reduction. — Iron  ores  are  always  reduced  in  the  blast  fur- 
nace, the  parts  and  operation  of  which  have  been  described  (Pars. 
53  and  57.     The  process  of  smelting  iron  is  very  simple,  as  the 
ores  used  are  oxides,  uncombined  with  other  metal?,  and  merely 
mixed  with  gangue,  which  is  removed  by  combining  with  the  flux 
in  the  charge.     The  simplicity  of  the  process  consists  in  the  fact 
that  all  of  the  chemical  changes  take  place  in  one  operation. 

The  important  changes  are  as  follows:  The  highly  heated  air 
.forced  in  at  the  tuyeres  at  once  spreads  through  the  charge  which 
fills  the  furnace.  Coming  in  contact  with  the  incandescent  fuel, 
the  oxygen  of  the  blast  and  the  carbon  of  the  fuel  unite,  forming 
COo.  The  C02  meets  more  carbon  as  it  rises  and  gives  up  part  of  its 
oxygen,  forming  CO.  This  is  a  powerful  reducing  agent  and,  with 
some  complexity  of  reaction,  it  reduces  the  ore,  and  at  the  same  time 
the  flux  combines  with  the  gangue.  Metallic  iron  and  slag  are  thus 
formed,  and  as  they  sink  into  the  fusion  zone,  both  melt  and  run 
down. 

In  the  intense  heat  of  the  fusion  zone,  some  of  the  compounds  of 
silicon,  sulphur  and  manganese,  and  usually  all  the  phosphorus 
compounds  are  decomposed,  and  these  elements  enter  the  molten 
iron.  At  the  high  heat  of  the  modern  blast  furnace  molten  iron 
also  dissolves  some  carbon,  hence  when  the  iron  settles  on  the  fur- 
nace hearth  it  has  carried  down  with  it  small  amounts  of  silicon, 
phosphorus,  sulphur,  manganese  and  carbon,  which  are  always  pres- 
ent in  ore,  flux,  or  fuel,  but  which  have  a  great  affinity  for  iron  and 
remain  with  it  when  tapped  from  the  furnace. 

92.  Pig  Iron. — The  product  of  the  blast  furnace  is  pig  iron. 
From  this  all  other  forms  of  iron  and  steel  are  now  made.     Some 
grades  of  pig  iron  are  selected,  and  without  further  change  are 
merely  re-melted  in  the  foundry  for  making  castings,  hence  it  has 
become  common  for  the  designations  "  pig  iron  "  and  "  cast  iron  " 
to  be  interchanged. 

All  pig  iron  contains  an  aggregate  of  about  7  per  cent  or  less  of 
the  five  substances,  carbon,  sulphur,  phosphorus,  silicon  and  man- 
ganese, and  the  grade  or  quality  of  pig  iron  for  various  uses  is  de- 
termined by  the  amounts  of  each  of  these  ingredients  contained 


IRON  AND  STEEL  71 

Iron  occasionally  takes  up  other  substances  in  smelting,  but  these 
are  usually  negligible. 

For  high-grade  uses  demanding  an  iron  of  superior  ductility  and 
chemical  purity,  a  limited  quantity  of  "  charcoal  iron  "  is  at  pres- 
ent smelted.  Ores  of  exceptional  purity  are  selected  (particularly 
free  from  sulphur  and  phosphorus)  and  are  smelted  with  charcoal 
fuel.  A  cold  blast  of  air  causes  the  iron  to  dissolve  less  carbon  than 
it  dissolves  in  the  higher  temperature  of  the  hot  blast,  also  a  lower 
smelting  temperature  lessens  the  introduction  of  other  ingredients 
into  the  iron,  hence  the  superiority  of  "  cold  blast  iron.7" 

The  name  "  pig  iron  "  comes  from  the  former  way  of  running 
iron  from  the  blast  furnace  along  channels  and  branch  channels,  in 
herring-bone  shape,  in  the  level  sand  bed  adjacent  to  the  furnace. 
The  iron  along  the  main  channel  was  called  the  sow,  and  that  in 
the  branch  channels  was  called  the  pigs. 

93.  Disposition  of  Iron  from  the  Blast  Furnace. — When  iron  is 
tapped  from  the  furnace,  it  is  the  practice  at  present  to  convey  it 
by  means  of  a  trough  or  trench  into  a  large  ladle,  even  if  it  is  to  be 
cast  into  pigs.  Fig.  16  shows  iron  flowing  along  a  trench  from  the 
furnace,  on  its  way  to  the  ladles,  and  Fig.  17  shows  the  metal  flow- 
ing into  ladles.  Large  ladles  hold  about  50  tons,  and  are  either 
supported  on  a  car  and  hauled  by  a  small  locomotive,  or  are  lifted 
and  transported  by  a  traveling  crane.  The  ladle  contents  may  be 
disposed  of  in  any  of  the  ways  below  stated,  depending  upon  the 
purpose  for  which  the  smelter  product  of  a  particular  composition 
may  be  suited. 

( 1 )  Poured  into  a  large  reservoir  called  a  "  mixer  "  which  main- 

tains a  supply  of  molten  metal  (designated  as  "hot"  or 
"direct"  metal)  for: 

(a)  Making  steel  by  the  open  hearth  process. 

(b)  Making  steel  by  the  Bessemer  process. 

(2)  Poured  into  pig  moulds  made  of  heavy  iron  to  be  re-melted 

later  for: 

(c)  Making  iron  castings  in  the  foundry. 

(d)  Making  wrought  iron  in  the  puddling  furnace. 

(e)  Uses  stated  in  items  (a)  and  (b). 


MECHANICAL  PROCESSES 


FIG.  16.— Base  of  a  Blast  Furnace  showing  iron  flowing  from  the 
furnace  along  trenches  conveying  it  to  ladles.  The  stream  is  directed 
along  the  trenches  by  the  gates  G.  When  the  flow  of  iron  from  the 
furnace  is  to  be  stopped,  the  "  mud  gun  "  H  is  swung  around  on  its 
crane  R  in  front  of  the  tapping  hole.  It  operates  a  piston  rod  by 
hydraulic  power  and  forces  a  cone  of  clay  into  the  tapping  hole 


FIG.  17.— Ladles  Receiving  Molten  Pig  Iron  from  Blast  Furnace 

Troughs. 


IRON  AND  STEEL  73 

94.  Grades  of  Pig  Iron.-— The  grade  of  iron  which  a  furnace  is 
producing  is  governed  within  certain  limits  by  the  chemical  make- 
up of  ore,  fuel,  and  flux,  but  the  composition  of  these  elements  of 
the  charge  is  not  always  uniform,  nor  are  heat  conditions  in  the 
furnace  always  the  same.     These  variations  give  rise  to  iron  of 
various  compositions,  within  certain  limits,  and  when  iron  is  cast 
into  pigs,  a  sample  from  each  heat  is  analyzed  chemically,  to  deter- 
mine the  per  cent  of  each  of  the  five  ingredients  named,  and  the 
iron  is  graded  from  this  analysis. 

In  the  old  way  of  casting  iron  into  pigs  in  the  sand  bed,  the  cast 
had  to  be  broken  up  to  be  removed.  This  gave  opportunity  to  in- 
spect the  fracture  and  judge  approximately  the  quality  of  the  iron 
from  its  carbon.  These  fractures  showed  either  grey,  mottled,  or 
white  color,  in  the  order  of  the  uncombined  carbon  which  the  iron 
contained,  and  by  these  colors  the  iron  could  be  graded  for  its  suit- 
ability for  different  uses.  The  grey  iron  is  soft  and  used  mostly 
in  the  foundry,  as  it  makes  excellent  castings  and  can  be  easily 
machined.  The  white  iron,  on  the  other  extreme,  is  hard  and 
brittle,  difficult  to  cut,  and  is  best  adapted  for  steel  or  wrought  iron 
making. 

Various  grades  of  pig  iron  are  named  from  the  locality  or  com- 
pany which  produces  them,  particularly  in  England. 

Buyers  of  pig  iron  now  purchase  their  iron  according  to  its 
chemical  composition,  and  not  according  to  its  trade  name,  nor 
according  to  inspection  of  fracture.  The  American  Society  for 
Testing  Materials  has  recommended  that  in  each  car  load  of  pig 
iron,  one  pig  in  each  four  tons  shall  be  selected  for  sampling  and 
analysis. 

II.  The  Classification,  Ingredients  and  Properties  of  Iron 
and  Steel. 

95.  The  Three  General  Classes. — It  is  essential  to  understand  the 
difference  between  the  several  classes  of  iron  and  steel,  and  the 
effects  of  the  substances  which  they  always  retain  from  the  blast 
furnace.    These  substances  are  frequently  spoken  of  as  impurities, 
but  some  of  them  are  always  more  or  less  desirable  in  the  iron  in 
giving  it  certain  properties.    It  may  be  stated  that  chemically  pure 
iron  is  not  known,  except  possibly  as  a  laboratory  curiosity. 


74  MECHANICAL  PROCESSES 

The  three  general  classes  of  iron  are  (1)  wrought  iron,  (2)  steel, 
and  (3)  cast  iron.  Within  each  class  there  are  many  grades,  due 
to  the  varying  quantities  of  the  substances  which  each  grade  con- 
tains. These  substances  affect  the  metal  adversely  or  otherwise 
according  to  their  quantity  and  the  use  for  which  the  metal  is 
desired. 

All  grades  and  classes  of  iron  and  steel  gradually  merge  one  into 
another,  and  the  difference  between  them  is  due  primarily  to  carbon. 
The  approximate  limitations  of  carbon  contained  by  each  class  are 
as  follows : 

Wrought  Iron   Trace  to     .08  per  cent 

Mild  Steel   (also  known  as  "  Ingot  Iron,"  "  Low  Carbon 

Steel,"  "  Soft  Steel ")    Trace  to  about  0.25  per  cent 

High  Carbon  Steel About  0.25  to  2.2     per  cent 

Cast  Iron *2.2  to  4.5     per  cent 

Carbon  in  iron  and  steel  has  a  direct  effect  upon  their  properties, 
and  other  elements  usually  contained  govern  somewhat  the  power 
of  the  metal  to  take  up  carbon,  and  their  influence  is  both  direct 
and  indirect.  Iron  and  steel  are  affected  similarly  by  the  same 
ingredients,  and  in  discussing  these  the  general  term  iron  is  meant 
to  include  steel. 

It  will  assist,  in  the  study  of  the  several  elements  taken  up  by 
iron,  to  regard  the  metal  in  its  molten  state  as  a  solvent  which  has 
a  stronger  tendency  to  dissolve  some  elements  than  others,  and 
which,  when  certain  elements  have  been  dissolved,  has  a  decreased 
or  an  increased  power  to  dissolve  other  elements. 

96.  Carbon  in  Iron. — When  iron  is  fused  in  smelting,  it  gets  its 
first  carbon,  the  amount  depending  upon  its  temperature,  and  upon 
the  manganese,  silicon  and  other  substances  present  in  the  furnace. 
This  amount  increases  with  the  temperature  and  is  influenced  in 
different  ways  by  the  other  substances  contained,  but  is  rarely  less 
than  1.8  per  cent.  When  the  metal  solidifies,  its  carbon  may  assume 
either  an  invisible  form,  called  combined  carbon,  in  which  case  the 

*  The  International  Association  for  Testing  Materials  has,  for  specific 
reasons,  based  upon  investigations  of  Messrs.  Carpenter  &  Keeling, 
recommended  that  the  line  be  drawn  between  steel  and  cast  iron  at 
2.20  per  cent  of  carbon. 


IRON  AND  STEEL  75 

metal  sh^ws  a  white  fracture ;  or  it  may  be  visible  in  the  fracture, 
giving  a  mottled  or  grey  color,  and  known  as  uncombined  carbon 
or  graphite.  The  condition  assumed  by  the  carbon  as  the  metal 
solidifies  depends  (1)  upon  the  rate  of  cooling,  and  (2)  still  more 
on  the  kind  and  quantity  of  the  other  substances  contained  by  the 
metal. 

As  with  other  solvents,  iron  forms  a  non-crystalline  mass  if 
cooled  rapidly,  and  none  of  the  carbon  is  precipitated,  thus  showing 
the  white  fracture  of  iron,  but  slow  cooling  allows  formation  of 
metal  crystals,  and,  if  the  carbon  is  above  3%,  some  of  it  separates 
as  uncombined  carbon. 

Carbon  renders  iron  and  steel  hard,  less  ductile  and  more  fusible, 
directly  according  to  the  amount  contained,  and  it  is  well  to  un- 
derstand that  a  small  alteration  in  the  amount  of  combined  carbon 
has  very  marked  effect  upon  the  metal,  while  a  moderate  alteration 
in  the  amount  of  uncomlined  carbon  has  very  little  effect. 

97.  Silicon  in  Iron. — Cast  iron  ordinarily  contains  silicon  up  to 
4%  or  slightly  more,  although  "  silicon  pig/'  the  form  in  which 
silicon  is  handled  for  foundry  and  similar  uses,  is  made  in  the  blast 
furnace  containing  up  to  18%  of  silicon;  and  ferro-silicons,  made 
by  the  electric  furnace,  may  contain  up  to  95%  of  silicon. 

Next  to  carbon,  silicon  is  most  important  in  determining  the 
suitability  of  cast  iron  for  foundry  use,  because  its  presence  up  to 
2%  assists  the  softness  and  fluidity  of  the  metal.  It  softens  the 
metal,  making  it  tough  and  less  brittle,  by  decreasing  the  per  cent 
of  combined  carbon,  which  acts  as  a  hardening  element.  Also,  in 
increasing  the  fluidity  of  molten  cast  iron,  silicon  contributes  to 
the  prevention  of  blow  holes  in  making  foundry  castings  by  allow- 
ing time  for  the  gases  formed  or  entrained  in  the  molten  metal  to 
escape. 

Beyond  2%,  silicon  renders  iron  weak  and  hard.  The  solution 
of  carbon  in  iron  is  rendered  more  difficult  by  the  presence  of 
silicon,  as  iron  dissolves  silicon  in  preference  to  carbon. 

98.  Sulphur  in  Iron. — This  element  is  particularly  objectionable, 
but  is  always  present  in  iron  and   steel,  rendering  them  brittle 
when  hot,  a  condition  known  as  "  red  short "  or  "  hot  short."    Iron 
and  steel  for  high-grade  forgings  must  not  contain  more  than  .04% 
of  sulphur,  although  for  castings  the  metal  may  safely  contain  up 


76  MECHANICAL  PROCESSES 

to  .15%.    Sulphur  in  iron  tends  to  cause  the  carbon  to  assume  the 
combined  form. 

99.  Phosphorus  in  Iron. — Neither  the  quantity  of  carbon  dis- 
solved in  iron  nor  its  condition  as  combined  or  uncombined  carbon 
is  much  affected  by  phosphorus,  but  this  element  has  the  effect  of 
hardening  iron  slightly.     It  is,  however,  highly  objectionable  in 
forged  iron  and  only  slightly  less  so  in  foundry  iron  for  castings, 
as  it  causes  brittleness  when  iron  is  cold,  a  condition  known  as 
"  cold  short,"  and  may  cause  the  metal  to  break,  when  worked  cold 
or  when  receiving  repeated  shocks  in  use.     It  should  not  exist  in 
iron  for  important  forgings  beyond  .06%,  nor  in  foundry  iron  for 
strongest  castings  beyond  .5%,  although  it  is  used  in  railroad  rails 
to  harden  them  against  wear.     Iron  high  in  phosphorus  does  not 
make  good  grate  bars  nor  other  castings  subjected  to  high  heat,  as  it 
renders  them  spongy. 

Phosphorus  renders  molten  iron  very  fluid  and  causes  it  to  take 
an  excellent  impression  of  the  mould,  hence  in  small  castings  where 
strength  is  not  the  first  requisite,  iron  may  be  used  containing  up 
to  1%  of  phosphorus. 

Neither  phosphorus  nor  sulphur  can  be  avoided  in  iron  making, 
and  both  are  difficult  to  eliminate.  The  best  means  of  keeping  them 
below  objectionable  amounts  is  to  select  ore  fuel  and  flux  for  smelt- 
ing which  are  as  free  as  possible  from  them,  although  materials 
for  the  smelter  are  seldom  ideal  and  cannot  always  be  selected  as 
desired. 

100.  Manganese  in  Iron. — The  smelting  process  always  leaves  in 
iron  a  small  amount  of  this  element.     Up   to   2%   it  increases 
tenacity  and  hardness,  but  beyond  that  amount  it  causes  brittleness. 
It  tends  to  eliminate  sulphur  and  neutralize  silicon,  hence  its  effect 
within  this  range  would  act  to  render  iron  less  hard  by  decreasing 
the  hardening  effects  of  these  elements.    Much  manganese  increases 
the  soluble  power  01  cast  iron  for  carbon. 

In  foundry  iron,  manganese  is  added,  if  not  already  present,  up 
to  about  1.5%  for  its  effect  in  making  a  hard,  close-grained  iron 
and  in  eliminating  sulphur  absorbed  during  re-melting  for  the  pur- 
pose of  casting. 

In  steel  making,  manganese  is  always  added  up  to  about  .05% 
for  improving  the  working  qualities  of  the  steel,  particularly  when 
hot. 


IRON  AND  STEEL  77 

The  extensive  use  of  manganese  as  an  ingredient  in  steel  making 
has  made  common  two  alloys  of  manganese  and  iron.  One,  known 
as  spiegel-eisen,  contains  from  1.5  to  about  20%  of  manganese, 
and  presents  a  brilliant  fracture.  The  other,  known  as  ferro-man- 
ganese,  contains  from  20  up  to  86%,  has  a  light  gray  fracture  and 
is  so  brittle  that  it  may  be  readily  pulverized  in  a  mortar.  Both 
of  these  products  are  obtained  from  the  oxide  of  manganese,  a 
mineral. 

101.  Properties  of  Cast  Iron. — Cast  iron  is  brittle,  non-elastic, 
and  the  easiest  fused  of  all  iron,  these  properties  varying  directly 
with  the  amount  of  combined  carbon  and  to  a  less  degree  with  the 
amount  of  uncombined  carbon  contained.     It  can   be   cast   into 
intricate  forms  and  has  the  advantage  of  expanding  upon  cooling, 
but  it  cannot  be  forged,  nor  united  by  the  usual  welding  process 
of  heating  and  hammering.     It  it  not  malleable  nor  ductile,  and 
cannot  be  hardened  like  steel,  because  it  contains  uncombined  car- 
bon.    It  has  either  a  crystalline  or  a  granular  fracture,  determined 
by  rapidity  of  cooling,  and  melts  at  about  2100°  F. 

102.  Properties    of    Wrought    Iron. — In    composition,    wrought 
iron  differs  from  cast  iron  and  steel  in  two  important  features,  viz. : 
(1)   In  having  had  removed,  as  an  essential  of  its  manufacture, 
the  greater  part  of  the  five  elements  usually  contained  in  iron.     In 
this  respect  it  is  near  the  composition  of  mild  steel.     (2)  In  con- 
taining, as  a  result  of  the  process  of  manufacture,  a  quantity  of 
slag  (usually  called  cinder)  which  surrounds  each  iron  crystal  in  a 
thin  sheath,  and  preserves  the  identity  of  the  crystal  as  a  fiber 
when  a  bar  of  wrought  iron  is  elongated  by  rolling  or  hammering. 
In  this  respect  it  differs  from  steel,  which  is  crystalline  and  with- 
out much  slag. 

The  chief  properties  of  wrought  iron  are  as  follows,  viz. : 

(a)  It  is  very  malleable  and  ductile,  and  can  be  readily  forged, 
particularly  when  heated. 

(b)  It  cannot  be  cast,  as  it  is  fusible  only  at  a  very  high  tem- 
perature (about  2800°  F.),  and  merely  becomes  pasty  at  the  usual 
furnace  temperatures,  though  because  of  this  quality  it  is  readily 
united  by  welding. 

(c)  It  cannot  be  hardened,  due  to  lack  of  carbon. 

(d)  If  pulled  apart,  the  fracture  shows  a  fibrous  break. 
-      6 


78  MECHANICAL  PROCESSES 

Wrought  iron  gets  its  name  from  the  fact  that  it  may  be  wrought 
into  various  shapes  readily  under  the  hammer;  also  it  is  called 
malleable  iron  in  England,  because  of  its  great  malleability,  but  it 
must  not  be  confused  with  malleable  castings,  also  called  malleable 
cast  iron  or  merely  malleable  iron  in  America. 

While  wrought  iron  and  mild  steel  resemble  each  other,  there  are 
certain  distinct  advantages  of  wrought  iron  which  cause  it  to  be 
retained  for  some  uses.  Among  its  advantages  are  (1)  it  welds 
better  than  does  steel,  (2)  lasts  longer  when  exposed  to  weather  or 
to  water,  (3)  is  better  to  resist  shock  and  vibration  (fatigue),  in 
use,  and  (4)  its  fibrous  structure  arrests  fracture,  as  its  breaking 
is  in  the  nature  of  a  gradual  tearing,  which  often  gives  warning  of 
a  dangerous  stress,  while  steel  breaks  suddenly. 

Among  the  disadvantages  of  wrought  iron  are,  ( 1 )  its  elastic  and 
tensile  strength  are  lower  than  those  of  steel,  (2)  and  its  produc- 
tion is  more  costly. 

103.  Properties  of  Steel. — When  steel  first  came  into  practical 
use,  its  distinguishing  characteristic  was  its  ability  to  harden  if 
heated  to  a  red  heat  and  cooled  suddenly,  as  in  water  or  oil.  Present 
methods  of  steel  making  have,  however,  brought  out  a  product  of 
iron  containing  too  little  carbon  to  harden  when  cooled  suddenly, 
yet  its  composition  differs  from  the  old  form  of  steel  only  in  con- 
taining less  carbon. 

Primarily,  the  differences  between  wrought  iron,  the  several 
grades  of  steel,  and  cast  iron  are  due  to  the  per  cent  of  carbon  in 
each  class  of  metal,  and  for  this  reason  steel  is  said  to  occupy  a 
place  between  wrought  iron  and  cast  iron.  However,  the  processes 
of  manufacture  give  steel  a  composition  and  a  molecular  structure 
which  affect  its  properties  aside  from  this  simple  relation.  The 
properties  of  steel  depend  primarily  upon  the  carbon  it  contains, 
influenced  by  the  kind  and  quantity  of  the  other  ingredients  (or 
impurities,  they  may  be  called),  and  further  influenced  by  the  cool- 
ing of  the  steel  from  its  molten  state.  This  last-named  influence 
determines  the  size  and  composition  of  the  crystals  which  steel 
assumes  upon  cooling. 

Despite  the  somewhat  complex  conditions  determining  the  prop- 
erties of  steel,  the  grades  of  steel  are  classed  according  to  their 
hardness  due  to  their  contained  carbon.  The  higher  the  per  cent 


IRON  AND  STEEL  79 

of  carbon,  the  greater  the  strength  and  brittleness,  and  the  less  the 
elongation  before  breaking.  The  grades  of  steel  merge  so  gradually 
one  into  another  that  only  two  classes  are  distinguished,  viz.,  mild 
steel  which  will  not  harden  when  suddenly  cooled,  and  high-carbon 
steel  which  will  harden  when  suddenly  cooled  from  a  red  heat. 
This  property  of  hardening  begins  to  show  when  the  steel  contains 
.25$  of  carbon  though  is  not  of  much  practical  use  in  hardening 
tools  until  the  carbon  has  reached  about  .75%  in  the  steel. 

A  quick  means  of  showing  whether  a  piece  of  iron  is  wrought 
iron  or  steel  is  to  place  it  in  a  somewhat  dilute  mixture  of  sul- 
phuric and  hydrochloric  acids,  after  it  has  been  cleaned  to  show  a 
metallic  surface.  Steel  shows  a  granular  and  wrought  iron  shows 
a  fibrous  structure  after  a  few  minutes  action  of  the  acid. 

The  conditions  determining  the  properties  of  iron  and  steel  can 
only  be  touched  upon  lightly  here,  and  the  pursuit  of  this  subject 
is  in  itself  a  special  study. 

III.  The  Manufacture  of  Wrought  Iron. 

104.  History  of  Wrought  Iron. — Wrought  iron  is  the  form  in 
which  iron  was  probably  first  known  to  man.  The  ancients  reduced 
it  directly  from  the  oxide  ores  in  small  furnaces,  using  charcoal  as 
fuel  and  depending  at  first  for  a  blast  upon  the  pressure  of  a  strong 
wind  to  force  air  through  a  tuyere  in  the  side  of  the  furnace. 
The  heat  generated  was  barely  sufficient  to  reduce  the  ore,  and  not 
high  enough  to  cause  an  absorption  of  carbon  to  any  degree,  nor  the 
decomposition  of  the  silicon,  phosphorous  and  manganese  com- 
pounds. The  iron,  mixed  with  cinder  and  slag,  was  taken  from  the 
furnace  in  a  pasty  state  (because  it  did  not  melt  at  the  temperature 
of  the  furnace)  and  was  hammered  to  squeeze  these  substances  out. 

This  process  was  improved  and  enlarged,  until  finally  the  blast 
furnace  was  developed.  As  the  degree  of  heat  in  the  reducing 
furnace  became  higher,  due  to  a  closed  furnace,  thicker  walls,  more 
tuyeres  and  more  rapid  combustion  of  the  fuel  by  improved  methods 
of  supplying  a  pressure  blast,  the  production  of  pig  iron  gradually 
resulted  in  place  of  wrought  iron. 

Wrought  iron  was  produced  from  the  ore  merely  because  the 
heat  was  not  high  enough  to  make  the  metal  take  up  carbon,  the 
absorption  of  which  would  have  changed  the  product  to  pig  iron. 


80  MECHANICAL  PROCESSES 

105.  Methods     of     Production. — This     method     of    producing 
wrought  iron  direct  from  the  ore  is  called  the  direct  method.     It 
it  still  used  to  a  small  extent  in  a  few  places  in  Europe  where  char- 
coal is  cheap,  but  its  output  is  not  important  in  the  commercial 
world.     The  method  by  which  most  of  the  wrought  iron  is  now 
produced  is  known  as  the  indirect  method.    It  is  so  named  because 
the  ore  is  first  smelted  to  produce  pig  iron,  and  this  is  then  con- 
verted into  wrought  iron. 

106.  The  Indirect  Process  of  Wrought-Iron  Making. — This  proc- 
ess consists  essentially  of  the  following  steps,  viz. : 

(1)  Melting  pig  iron  in  a  form  of  reverberatory  furnace  called 
a  puddling  furnace,  and  burning  out  the  impurities  principally  by 
oxygen  supplied  from  iron  oxides. 

(2)  Subjecting  the  product  of  the  furnace,  after  its  removal 
therefrom  and  while  in  a  hot  and  plastic  state,  to  mechanical  treat- 
ment to  press  out  furnace  slag. 

(3)  Cutting  into  short  pieces  the  bars  of  impure  iron  resulting 
from  the  preceding  step,  binding  together,  re-heating,  then  ham- 
mering or  rolling.     This  eliminates  more  slag,  welds  the  several 
pieces  of  the  mass  thoroughly,  and  shapes  it  into  plates  or  bars  for 
market. 

Carbon  and  other  impurities  are  seldom  entirely  removed,  but 
are  merely  greatly  reduced  in  quantity.  It  is  impossible  to  burn 
out  carbon  and  other  impurities  without  also  burning  some  of  the 
iron. 

107.  The  Puddling  Furnace. — Fig.  18  shows  two  sections  of  a 
double  puddling  furnace,  built  double  to  save  space,  building  mate- 
rial and  heat.     This  furnace  is  built  of  common  brick,  and  lined 
with  refractory  brick.     It  is  held  together  by  vertical  iron  braces 
spaced  along  the  sides  and  connected  across  top  and  bottom  by  tie 
rods. 

A  particular  feature  of  the  puddling  furnace  is  its  hearth.  Be- 
side forming  a  basin  for  holding  the  molten  contents  of  the  furnace, 
the  materials  of  the  hearth  have  an  essential  chemical  purpose  in 
assisting  the  changes  brought  about  by  the  process. 

The  foundation  of  the  hearth  is  three  cast-iron  plates  resting  on 
masonry  supports.  Hollow  cast-iron  air-chambers,  A  A,  rest  on 
these  plates  and  extend  through  the  sides  of  the  furnace,  opening 


IROX  AND  STEEL 


81 


into  the  air.     These  strengthen  the  ends  of  the  hearth  and  assist 
greatly  in  relieving  the  fire  and  flue  bridges  of  the  intense  heat. 

The  hearth  is  made  of  furnace  slag  and  iron  ore.  This  slag  is 
composed  mainly  of  iron  oxide  and  silica  and  is  called  cinder.  The 
hearth  is  prepared  by  fusing  large  and  small  lumps  of  ore  and 
cinder  upon  the  plates  to  a  depth  of  about  6  inches.  The  sides  of 


FIG.  18. — Double  Puddling  Furnace. 

the  hearth  basin  are  also  formed  of  lumps  of  iron  oxide,  fused  to- 
gether by  the  heat  of  the  furnace.  Hoop  iron  is  burned  to  an  oxide 
over  this  mass  to  give  it  an  even  surface  of  pure  oxide. 

The  materials  of  which  the  hearth  and  its  sides  are  prepared  are 
designated  as  the  fettling  of  the  furnace.  They  are  gradually  con- 
sumed as  a  part  of  the  operation  of  the  furnace  and  must  be  re- 
newed occasionally. 


82  MECHANICAL  PROCESSES 

The  hearth  materials  are  kept  from  melting  during  the  operation 
of  the  furnace  by  the  radiation  of  heat  from  .the  plates  on  which 
it  is  built. 

108.  Puddling-Furnace  Operation. — Having  prepared  the  hearth 
and  brought  the  furnace  to  a  good  heat,  a  charge  of  about  1500 
Ibs.  of  pig  iron  is  thrown  in  at  the  working  door,  and  with  it  is 
charged  a  quantity  of  cinder  or  squeezer  scale. 

(1)  The  door  is  closed  tightly,  and  the  heat  is  so  regulated  that 
the  iron  and  the  cinder  become  pasty  and  melt  down  together. 
This  requires  about  30  minutes,  and  is  called  the  melting-down 
stage. 

(2)  After  the  charge  has  been  melted  and  the  iron  and  cinder 
well  mixed,  the  clearing  stage  follows.     The  puddler's  helper  uses 
an  iron  bar  with  a  bent  end  to  stir  the  whole  charge  thoroughly, 
working  through  the  hole  in  the  door.    The  stirring  brings  the  im- 
purities of  the  iron  into  contact  with  the  oxides  of  the  hearth  and 
of  the  charge,  and  these,  assisted  by  any  oxygen  coming  from  the 
air  which  enters  through  the  fire  box,  oxidize  the  remaining  silicon, 
manganese,  and  a  further  amount  of  the  phosphorus.     During  this 
stage,  the  furnace  is  kept  very  hot.     A  slag  is  formed,  containing 
the  oxidized  impurities  and  much  iron  oxide. 

(3)  The  next  step  is  the  boil,  from  which  this  whole  process 
gets  its  name  of  "pig  boiling."    This  lasts  about  30  minutes  and 
the  operation  removes  carbon  and  the  remainder  of  the  phosphorus. 
During  this  stage  the  chimney  damper  is  lowered  and  the  working 
door  opened  to  reduce  combustion  and  produce  an  oxidizing  flame. 
The  charge  is  stirred  thoroughly  and  constantly  with  the  hoe  or 
rabble   (or,  to  use  the  expression  of  puddling,  is  rabbled).     This 
vigorous  action  brings  the  carbon  of  the  metal  in  contact  with  the 
iron  oxides   of  the   hearth   and  the  charge,   causing  carbon   and 
oxygen  to  unite,  forming  CO,  which  bubbles  violently  from  the 
surface  of  the  molten  charge.     This  bubbling  causes  the  lighter 
slag  to  boil  over  the  side  of  the  basin  and  flow  from  the  furnace, 
carrying  with  it  many  of  the  oxidized  impurities.      Sulphur  is 
eliminated  mostly  as  iron  pyrites  in  the  slag  boil.     As  the  carbon 
burns  out,  the  charge  becomes  more  and  more  quiet. 

This  removal  of  the  carbon  having  lowered  greatly  the  melting 
temperature  of  the  iron,  small  masses  of  plastic  metal  begin  to 


IRON  AND  STEEL 


83 


collect  just  as  butter  collects  in  the  churn.  The  iron  is  said  to 
"  come  to  nature  "  in  thus  collecting. 

(4)  In  the  final  stage,  the  puddler  gathers  these  masses  into 
balls  of  about  150  Ibs.  each,  called  blooms,  or  puddle  balls.  The 
furnace  temperature  is  gradually  raised,  and  the  puddle  balls  are 
brought  to  a  welding  heat.  The  puddler  presses  them  sufficiently 
to  make  them  hold  together  and  they  are  then  removed  from  the 
furnace.  After  their  removal  the  excess  of  slag  is  tapped  out  and 
the  furnace  is  ready  for  a  new  charge. 

Each  heat  requires  about  2  or  2y2  hours. 

109.  Treatment  of  Puddle  Balls. — The  furnace  treatment  just 
described  burns  out  almost  all  of  the  usual  impurities  in  iron,  but 


FIG.  19. 

this  treatment  produces  a  slag  or  cinder  of  iron  oxide  and  silica 
which  mixes  with  the  iron  and  forms  a  sheath  around  each  iron 
crystal. 

When  the  puddler  has  formed  a  ball  for  removal  from  the  fur- 
nace, his  helper  takes  it  out  by  means  of  a  pair  of  heavy  tongs  sus- 
pended from  an  overhead  trolley,  and  pushes  it  over  to  the  squeezer. 

This  machine  (Fig.  19)  consists  of  a  heavy  cast-iron  casing  B, 
within  which  revolves  a  rough-surfaced  cast-iron  cylinder  C.  The 
space  A  between  the  cylinder  and  the  casing  is  wide  at  one  opening 
and  somewhat  narrower  at  the  other.  The  cylinder  is  constantly 
revolving  slowly,  and  when  the  puddle  ball  starts  at  D,  it  is  rolled 
and  squeezed  until  it  emerges  at  E.  This  operation  presses  out 


84 


MECHANICAL  PROCESSES 


masses  of  cinder  with  more  or  less  violence  and  noise.     Fig.  20 
shows  a  squeezer  for  heavy  work. 


FIG.  20.— Squeezer  for  400-lb.  Bloom. 


FIG.  21.— Puddle  Rolls. 


IRON  AXD  STEEL 


85 


The  bloom  emerging  at  E,  Fig.  19,  still  at  a  high  heat,  is  immedi- 
ately grasped  with  heavy  tongs  and  started  through  the  rolls  shown 
in  Fig.  21.  The  end  of  the  bloom  is  presented  first  to  the  largest 
pass,  I,  and  when  it  has  gone  through  this  pass,  it  is  sent  back  over 
the  top  of  the  upper  roll  and  is  in  turn  run  through  the  entire 
seven  passes.  Some  cinder  is  pressed  out,  and  the  iron  particles 
are  pressed  into  a  more  tenacious  mass.  The  last  pass,  which  is 
near  the  center  of  the  rolls,  leaves  the  bar  about  6  inches  wide  and 
less  than  an  inch  thick. 

This  product  is  known  as  muck  bar  or  puddled  bar.  The  rolls 
have  elongated  the  iron  crystals,  giving  the  bar. a  fibrous  structure, 
and  each  fiber  is  enclosed  in  a  thin  sheath  of  cinder,  with  streaks 
of  cinder  between  many  of  the  fibers. 

110.  Re-heating  and  Welding  Muck  Bar  into  Wrought  Iron. — 
Muck  bar  still  contains  too  much  cinder  and  is  too  lacking  in  homo- 
geneity for  use. 


FIG.  22. — Re-heating  Furnace  used  in  Making  Wrought  Iron. 

When  cold,  it  is  cut  into  lengths  of  about  3%  feet.  Bundles 
measuring  about  20  inches  wide  by  20  inches  high  are  then  made 
up  of  muck-bar  lengths  and  wrought-iron  scrap.  Each  bundle, 
called  a  pile,  is  held  together  by  a  wrapping  of  heavy  wire  or  thin 


86  MECHANICAL  PROCESSES 

iron  bands.  A  number  of  these  piles  are  shown  on  the  right  in 
Fig.  22,  ready  for  wrapping.  These  piles  are  placed  in  a  re-heating 
furnace  of  the  general  type  shown  in  Fig.  22,  heated  about  three 
hours  until  they  reach  welding  heat  and  are  then  taken  out  one  at 
a  time,  and  quickly  passed  through  heavy  rolls  adjacent  to  the 
furnace. 

A  few  passes  back  and  forth  through  these  rolls,  called  the  rough- 
ing rolls,  squeeze  out  a  great  amount  of  the  remaining  slag  with 
much  explosion  and  noise  and  thoroughly  weld  together  the  several 
pieces  composing  the  pile.  The  rolls  then  work  the  mass  down  to 
approximate  shape  as  plates  or  bars  and  it  is  then  conveyed  along 
the  roller  table  to  the  finishing  rolls  by  which  it  is  shaped  into 
sheets,  bars,  or  rods  as  may  be  required. 

For  rapidity  and  economy  of  handling  piles  there  are  several 
re-heating  furnaces  and  at  least  one  set  of  roughing  rolls  placed 
along  the  arc  of  a  circle,  at  the  center  of  which  is  a  heavy  electric- 
ally operated  crane  so  mounted  with  a  horizontal  arm  that  piles 
may  be  transferred  from  the  furnaces  to  the  roller  table  with  a 
minimum  loss  of  time. 

111.  Rolls  for  Shaping  Wrought  Iron. — Fig.  23  shows  the  gen- 
eral type  of  rolls  used  for  wrought-iron  piles.  This  machine  is 
very  simple,  and  consists  essentially  of  three  chilled  cast-iron  rolls 
A,  B,  C,  mounted  in  a  frame  DD  (called  the  housings)  so  that 
the  axes  of  the  rolls  are  horizontal  and  one  above  another.  Kolls 
A  and  C  are  driven  by  a  large  engine  through  the  connecting  shafts 
G  and  H,  and  the  middle  roll  is  free.  The  bearings  of  the  lower 
-roll  are  fixed  in  the  housings  of  the  machine,  the  bearings  of  the 
middle  roll  are  free  to  raise  or  lower,  and  those  of  the  upper  roll 
are  raised  or  lowered  by  long  screw  rods  worked  simultaneously  by 
the  gearing  on  top  of  the  machine.  In  this  way  the  space  between 
the  rolls  is  adjusted  readily  by  the  operator  to  suit  the  thickness 
to  which  the  iron  is  to  be  reduced  as  it  passes  through. 

The  mass  of  iron  which  passes  back  and  forth  through  these  rolls 
is  handled  by  a  roller  table  on  each  side  of  the  machine.  The  roller 
table  on  one  side  is  shown  in  the  foreground.  Its  rollers  are  con- 
nected by  gearing  (not  shown)  so  that  all  rollers  may  be  made  to 
revolve  in  either  direction  simultaneously.  As  the  table  now  rests, 
it  shows  a  plate  L  which  has  just  come  through  between  the  middle 


IRON  AND  STEEL 


87 


FIG.  23. — Rolls  for  Making  Wrought  Iron  Plates. 


88  MECHAXICAL  PROCESSES 

and  lower  rolls.  In  order  to  run  this  plate  back  between  the  middle 
and  upper  rolls,  the  end  of  the  table  is  lifted  by  hydraulic  power. 
The  table  end  having  been  lifted  to  the  required  height,  its  rollers 
are  reversed  and  the  plate  is  conveyed  into  the  rolls  of  the  machine. 

Houghing  and  finishing  rolls  are  of  similar  construction,  but  the 
former  is  a  heavier  machine  than  the  latter.  Most  the  shaping  is 
done  in  the  roughing  rolls  to  save  the  smoother  surface  of  the 
finishing  rolls  for  the  more  careful  work  they  have  to  do  in  finish- 
ing plates  to  a  smooth  surface  and  to  uniform  thickness. 

A  machine  for  rolling  bars  or  rods  has  passes  in  the  rolls  similar 
to  those  in  the  puddle  rolls  in  Fig.  21. 

When  material  has  been  rolled  to  the  shape  and  size  required,  it 
is  carried  by  the  roller  table  to  another  part  of  the  shop  where  it 
is  inspected  for  defects,  and  is  then  cut  by  the  power  shears  to  the 
required  dimensions. 

IV.  The  Manufacture  of  Steel. 

112.  History  of  Steel. — The  first  known  steel  was  possibly  pro- 
duced accidentally  by  the  primitive  method  which  smelted  wrought 
iron  direct  from  the  ore.  The  increase  of  the  degree  of  heat  in  the 
primitive  smelting  furnace  caused  the  iron  to  become  hot  enough  to 
absorb  in  a  combined  form  that  quantity  of  carbon  which  gave  it  a 
new  property.  It  was  found  that,  although  this  newly  discovered 
grade  of  metal  had  to  a  greater  or  less  degree  the  malleability  of 
wrought  iron  when  cooled  slowly,  it  further  had  the  property  of 
becoming  hard  and  brittle  wThen  cooled  suddenly  from  a  red  heat. 

The  uses  of  steel  made  in  this  primitive  way  must  have  been  very 
limited  because  of  the  uncertain  means  of  producing  it. 

Not  until  the  cementation  process  of  steel  making  was  discovered 
and  developed,  about  1770,  did  steel  become  a  fairly  dependable 
and  practical  product,  although  its  uses  remained  confined  for  a 
long  time,  by  the  limitations  of  this  process,  to  the  making  of 
cutlery,  edged  tools,  and  special  parts  of  machinery.  The  cementa- 
tion process  could  not  supply  steel  for  a  wider  field  of  use  because 

(1)  the  product  in  large  quantities  lacked  uniform  composition; 

(2)  it  could  not  always  be  depended  upon  when  strength  was  of 
first  importance,  and  (3)  its  production  was  expensive. 


IRON  AND  STEEL  89 

The  need  for  a  steel  of  uniform  quality,  dependable  strength, 
and  low  cost  in  large  quantities,  led  to  investigations  along  other 
lines  of  possibility  in  steel  production.  The  puddling  process,  as 
used  in  wrought-iron  making,  was  tried  for  steel  making,  with  the 
idea  that  the  burning  out  of  carbon  should  be  stopped  when  enough 
remained  in  the  charge  to  give  the  grade  of  steel  desired,  but  this 
was  not  satisfactory  because  the  stopping  of  the  oxidizing  process 
at  the  point  to  retain  the  necessary  amount  of  carbon  left  too  much 
of  the  other  impurities  in  the  metal. 

Finally,  in  1856,  Sir  Henry  Bessemer  made  public  the  process 
which  bears  his  name.  In  1868  Sir  Wm.  Siemens  in  England  and 
Messrs.  Martin  in  France  perfected  the  Siemens  and  the  Siemens- 
Martin  processes  (almost  identical)  which  are  developed  from  the 
puddling  process  for  wrought  iron.  These  processes  have  revo- 
lutionized the  manufacture  of  steel,  and  have  so  extended  its  limits 
in  regard  to  its  carbon  content,  that  a  new  definition  of  the  product 
became  necessary,  particularly  as  mild  steel  cannot  be  hardened  by 
sudden  cooling. 

It  was  early  discovered,  in  the  use  of  these  processes,  that  a 
reliable  steel  could  not  be  made  from  pig  iron  containing  more 
phosphorus  or  sulphur  that  the  steel  should  contain,  because  these 
impurities  do  not  remain  oxidized  in  a  furnace  or  converter  with 
a  silica  lining,  as  then  used,  and  therefore  could  not  be  disposed  of 
with  the  slag.  Silicious  materials  are  acid  materials,  and  they  re- 
duce oxidized  phosphorus  and  sulphur  as  soon  as  it  is  formed,  caus- 
ing these  impurities  to  re-enter  the  steel.  The  use  of  silica  linings 
in  the  furnace  and  converter  classed  these  processes  as  acid  proc- 
esses of  making  steel.  This  limitation  of  the  newly  discovered 
processes  restricted  them  to  the  use  of  pig  iron  low  in  phosphorus 
and  sulphur,  and  this  restriction  caused  investigators  to  seek  and 
develop  the  basic  method  of  steel  making.  This  method  differs 
from  the  acid  process  primarily  in  having  a  lining  of  basic  material 
for  the  furnace  and  converter.  Such  a  lining  permits  the  use  of  a 
lime  flux,  which  will  remove  phosphorus  and  surphur,  while  a  silica 
lining  will  not  permit  the  use  of  a  lime  flux,  because  chemical 
action  between  lime  and  silica  would  soon  disintegrate  the  furnace 
or  converter  lining. 


90  MECHANICAL  PROCESSES 

113.  The  Cementation  Process. — By  this  process,  wrought-iron 
bars  are  converted  into  steel.  Alternate  layers  of  sifted  wood  char- 
coal and  iron  bars  are  placed  in  fire-brick  basins  or  "  pots/'  the  tops 
of  which  are  made  air  tight  with  a  layer  of  clay.  This  prevents 
burning  the  charcoal.  The  pots  are  then  heated  in  a  large  furnace. 
Maximum  heat  is  reached  in  about  48  hours,  and  this  is  continued 
for  8  to  12  days.  The  fire  is  then  allowed  to  die  out  and  the  bars  are 
removed  when  cold. 

The  high  temperature  has  caused  the  iron  to  absorb  the  carbon 
in  sufficient  quantity  to  change  it  into  steel. 

The  product  thus  obtained  is  called  blister  steel  because  the  bars 
are  covered  with  blisters  as  a  result  of  the  process.  This  steel  is 
not  yet  ready  for  use,  as  the  carbon  is  very  unequally  distributed  in 
it,  making  some  spots  very  hard  while  the  interior  remains  soft. 

To  correct  this  lack  of  homogeneity  the  blister  steel  is  further 
treated  by  one  of  the  two  f olloAving-named  processes : 

(1)  Cut  or  broken  into  small  pieces,  melted  in  covered  crucibles, 
and  poured  into  ingots  suitable  for  rolling  or  forging  to  the  shape 
desired.     This  equalizes  the  distribution  of  carbon  and  any  other 
elements  in  the  steel,  gets  rid  of  the  slag  or  cinder  which  formed  a 
part  of  the  wrought  iron,  and  makes  a  very  superior  grade  of  steel. 
This  is  known  as  crucible  steel. 

(2)  Cut  into  suitable  lengths,  piled,  welded  and  rolled  as  in  the 
case  of  muck  bar.    This  process  helps  to  average  up  the  distribution 
of  carbon  in  the  steel,  particularly  when  several  times  repeated,  but 
it  does  not  make  the  steel  homogeneous,  as  when  melted  in  the 
crucible,  and  each  repetition  of  heating  and  welding  adds  to  the 
expense  of  the  product.    This  product  is  known  as  shear  steel. 

The  cementation  process  has  practically  passed  into  history, 
except  that  its  use  continues  in  some  place  in  Europe,  particularly 
in  Sheffield,  England,  where  it  has  been  long  in  vogue,  and  much 
skill  has  been  acquired  in  using  it.  Steel  is  there  made  by  this 
process  from  the  purest  wrought  iron  for  a  superior  grade  of 
cutlery. 

The  crucible  part  of  the  process,  however,  is  still  retained,  as  will 
be  outlined  later  on,  and  is  an  important  branch  of  steel  making. 


IRON  AXD  STEEL  91 

114.  Present  Processes  of  Steel  Making. — At  present  there  are  in 
extensive  use  three  processes  of  steel  making.     These  are,  in  order 
of  the  annual  quantity  of  steel  produced  by  each : 

(1)  The  Bessemer  process. 

(2)  The  open-hearth  process  (Siemens  and  Siemens-Martin). 

(3)  The  crucible  process. 

Each  process  is  particularly  adapted  to  removing  the  impurities 
from  certain  grades  of  iron,  and  also  to  producing  certain  grades 
of  commercial  steel.  The  Bessemer  and  open-hearth  processes  have 
made  possible  a  low-carbon  steel  (mild  steel)  which  finds  extensive 
use  as  a  structural  material  in  buildings,  bridges,  hulls  of  vessels, 
steel  rails,  etc.  This  material  is  stronger  and  more  uniform  in 
quality  than  is  wrought  iron,  which  was  formerly  the  only  suitable 
material  for  these  uses.  The  Bessemer  process  is  the  least  expensive 
in  operation,  and  the  quality  of  its  product  depends  upon  the  grade 
of  pig  iron  used.  It  is,  however,  being  gradually  displaced  by  the 
open-hearth  process  because  of  the  diminishing  quantity  of  ores 
suitable  for  supplying  pig  of  the  required  composition. 

High-carbon  steel,  limited  in  use  to  tool  making,  springs,  and 
for  special  needs  in  which  extreme  hardness  is  an  important  feature, 
is  made  by  the  crucible  process.  Of  the  three  processes,  the  crucible 
process  produces  the  highest  grade  and  most  expensive  steel. 

115.  The  Bessemer  Process. — This  process  converts  pig  iron  into 
steel  by  blowing  cold  air  through  the  molten  metal  to  burn  out  the 
carbon.    After  the  carbon  is  removed  (and  incidentally  some  other 
impurities  are  removed),  and  the  air  blast  stopped,  enough  carbon 
is  re-introduced  into  the  charge  to  give  the  steel  the  amount  re- 
quired. 

This  operation  is  carried  on  in  a  large  vessel  called  a  converter, 
a  view  of  which,  partly  in  cross  section,  is  shown  in  Fig.  24.  The 
shell  of  the  converter,  marked  D,  is  built  of  steel  plates  in  three 
sections,  held  together  by  brackets  E.  To  the  bottom  is  bolted  two 
castings  J  and  K  which  form  a  hollow  receptacle  called  the  blast 
box  or  wind  box.  Two  other  plates  may  be  seen  in  the  bottom,  the 
upper  serving  to  strengthen  the  bottom,  and  the  lower,  marked  L, 
serving  to  hold  the  tuyeres  M  in  place.  The  shell  is  lined  for  the 
acid  process  with  ganister,  and  for  the  basic  process  (not  used  in 


92  MECHANICAL  PROCESSES 

America)   with  magnesite,  chromite  or  dolomite.     The  lining  is 
marked  C. 

The  vessel  is  supported  by  an  encircling  band  G,  which  carries 
two  trunnions  BB,  by  means  of  which  it  can  be  tilted  when  neces- 


•M 


FIG.  24. — Bessemer  Converter. 

sary.  One  trunnion  is  solid,  and  carries  a  large-toothed  wheel  A 
to  which  is  geared  the  rotating  mechanism.  The  other  trunnion 
is  hollow  to  afford  a  means  of  conveying  air  to  the  blast  box  K, 
through  the  pipe  H.  The  small  sketch  M  at  the  side  shows  one  of 
the  tuyeres,  made  of  refractory  material,  which  conveys  air  from  the 
box  to  the  interior  of  the  converter. 


IRON  AND  STEEL  93 

116.  Operation  of  the  Converter. — The  essentials  of  operating 
an  acid  converter  are  here  given.  The  operation  for  the  basic 
method  is  but  slightly  different. 

After  the  converter  has  been  emptied  of  a  charge,  the  vessel  is 
revolved  another  quarter  of  a  turn  until  it  is  upside  down.  In  this 
position  it  rests  for  a  moment  to  drain  out  the  excess  of  slag,  and 
another  quarter  revolution  places  the  vessel  horizontally.  In  this 
position  it  receives  a  new  charge.  Ten  tons  or  more  of  metal  are 
brought  over  from  the  mixer  in  a  large  ladle  and  poured  into 
the  converter.  Cranes  *  and  other  lifting  appliances  handle  the 
ladle  and  other  movable  equipment,  and  all  the  movements  of  the 
converter  are  managed  by  mechanical  appliances,  handled  by  an 
operator  on  a  high  platform  at  a  safe  distance  from  its  heat. 
Metal  poured  into  the  mixer  is  always  hot  enough  to  remain  fluid 
for  an  hour  or  more  and  it  needs  no  re-heating  when  conveyed  to 
the  converter. 

The  converter,  with  its  new  charge,  is  now  revolved  to  an  upright 
position,  and  the  air  blast  is  turned  on  just  as  soon  as  the  metal 
begins  to  reach  the  tuyeres,  to  prevent  it  flowing  into  the  blast  box. 
The  air  pressure  is  about  20  or  25  Ibs.  per  square  inch,  sufficient  to 
push  through  the  molten  metal. 

The  chemical  part  of  the  operation  at  once  begins  when  the  air 
enters  the  molten  metal,  and  a  yellow  flame  of  burning  impurities, 
accompanied  by  a  profuse  shower  of  sparks  of  burning  iron,  issues 
from  the  mouth  of  the  converter.  Silicon  and  iron  are  first  at- 
tacked by  the  oxygen,  and  these  form,  when  oxidized,  a  slag  which 
tends  to  rise,  but  is  kept  more  or  less  agitated  and  mixed  with  the 
charge.  After  the  silicon  is  burned  out,  the  carbon  is  next  attacked, 
and  the  formation  of  carbonic  oxide  causes  a  violent  bubbling  of 
the  charge,  a  stage  known  as  the  boil.  The  small  quantity  of 
manganese  usually  present  is  now  oxidized,  and  passes  into  the  slag. 

After  about  20  minutes,  the  flame  from  the  mouth  of  the  con- 
verter has  about  died  out,  indicating  the  complete  oxidation  of  car- 
bon, silicon  and  manganese.  A  continuation  of  the  blast  would 
ruin  the  charge  of  metal  by  filling  it  with  iron  oxide.  The  blow  is 

*  Figs.  25  and  27  show  cranes  and  appliances  for  handling  large 
ladles.  Each  of  these  views  shows  a  ladle  suspended  from  the  crane. 

7 


94  MECHANICAL  PROCESSES 

then  stopped,  but  just  before  doing  this,  the  converter  is  turned 
horizontal  to  prevent  metal  entering  the  tuyeres.  Little,  if  any, 
of  the  sulphur  and  phosphorus  originally  in  the  iron  are  removed, 
because  in  the  presence  of  the  silicious  lining  these  impurities  can- 
not remain  oxidized. 

After  the  blow  the  charge  consists  of  molten  iron  without  carbon 
silicon  or  manganese,  but  it  contains  phosphorus,  sulphur  and  iron 
oxide.  Enough  carbon  must  now  be  supplied  to  produce  the  kind 
of  steel  desired,  also  the  iron  oxide  and  gases  mixed  with  the  charge 
as  a  result  of  the  blow  must  be  removed,  so  far  as  can  be  done. 
These  are  accomplished  by  adding  to  the  charge  about  10$  of  ferro- 
manganese.  This  is  melted  in  a  small  cupola  near  the  converter, 
or  may  be  thrown  cold  into  the  converter  in  small  quantities.  The 
quantity  and  composition  of  the  ferro-manganese  must  be  so  ad- 
justed that  the  carbon  therein  will  give  the  converter  contents  just 
the  needed  amount,  and  the  quantity  of  manganese  must  be  suffi- 
cient to  reduce  the  iron  oxide  and  also  consume  the  free  oxygen 
absorbed  in  the  charge,  the  oxide  of  manganese  so  formed  rising 
into  the  slag.  The  slight  agitation  caused  by  these  reactions  helps 
to  expel  inert  gases  from  the  charge. 

The  stopping  of  the  blow  allows  the  charge  to  become  quiet,  and 
most  of  the  slag  and  gases  rise  to  the  surface.  After  the  ferro- 
manganese  has  been  stirred  in  thoroughly  (which  must  be  done 
promptly,  as  the  metal  must  not  become  chilled)  the  process  is 
completed  by  tilting  the  converter  and  pouring  its  contents  into  a 
large  ladle,  previously  heated  inside  by  a  charcoal  fire  or  an  oil 
flame.  The  greater  part  of  the  slag  flows  from  the  converter  into 
the  ladle  and  floats  on  the  surface  of  the  metal,  affording  it  pro- 
tection against  oxidation  and  rapid  cooling.  Some  slag  sticks  to 
the  converter'  lining.  This  protects  the  lining,  assists  in  the  con- 
verter reactions  of  the  next  charge,  and  retains  much  heat. 

117.  Pouring  the  Steel  into  Moulds. — The  ladle  is  at  once  con- 
veyed by  the  crane  to  a  row  of  large  cast-iron  ingot  moulds,  and  the 
metal  is  poured,  or  "  teemed,"  into  them  as  shown  in  Fig.  25.  Most 
large  ladles  are  now  poured  from  a  hole  in  the  bottom,  but  with 
ladles  poured  over  the  edge,  care  must  be  taken  to  skim  away  the 
slag  to  keep  it  from  going  into  the  mould.  The  slag  is  later  poured 


IRON  AND  STEEL 


95 


96  MECHANICAL  PROCESSES 

from  the  ladle  into  a  steel-bodied  slag  car  and  conveyed  to  the 
dump.  The  crane  moves  the  ladles  readily  along  the  row  of  moulds. 
In  this  view  the  moulds  are  filled  through  a  clay-lined  iron  pipe, 
or  "  runner,"  leading  into  the  bottom  of  each  mould.  These  run- 
ners are,  in  this  view,  behind  the  moulds.  The  moulds  are  not 
lined  nor  are  they  previously  heated,  but  ladles,  pipes,  troughs,  and 
other  refractory  lined  holders  or  conveyers  of  molten  metal  must 
be  heated  and  must  never  contain  any  moisture  when  metal  is 
poured  into  them. 

The  subsequent  treatment  of  the  ingots  produced  in  these  moulds 
is  described  in  the  next  chapter. 

118.  Features  of  the  Bessemer  Process. — Pig  iron  of  a  certain 
range  of  composition  must  be  selected  for  this  process.     It  must 
not  contain  more  phosphorus  nor  sulphur  than  is  allowable  in  the 
steel,  as  these  elements  are  not  burned  out  in  the  acid  Bessemer 
process.    Silicon  is  desirable  to  increase  the  heat  in  the  charge  when 
it  burns  in  the  converter,  and  its  is  also  the  chief  slag  producer, 
although  too  much  silicon  would  unduly  prolong  the  blow  while 
burning  it  out  and  this  prolonged  oxidation  would  consume  much 
iron. 

The  converter  charge  is  considerably  increased  in  temperature  by 
the  oxidation  from  the  blast  and  it  may  become  at  times  so  hot 
that  the  chemical  reactions  are  upset,  and  much  iron  is  consumed. 
To  reduce  the  temperature,  either  a  quantity  of  steel  scrap  of  cor- 
rect composition  is  thrown  into  the  converter  during  the  blow,  or 
steam  is  forced  through  with  the  air,  absorbing  heat  as  it  is  de- 
composed in  the  charge. 

Bessemer  steel  is  not  regarded  as  the  equal  of  open-hearth  or 
crucible  steels  in  purity,  as  the  removal  of  impurities  is  under 
better  control  in  the  two  last-named  processes.  The  Bessemer 
product  is  used  for  railroad  rails,  structural  steel  for  buildings, 
steel  castings,  forgings,  and  other  purposes  where  the  strength  of 
the  steel  is  not  put  to  its  supreme  test. 

119.  The  Open-Hearth  Process. — This  and  the  Bessemer  process 
convert  pig  iron  into  steel  by  first  burning  the  impurities  from  the 
molten  iron,  but  the  equipment  used  in  the  open-hearth  process 
differs  considerably  from  that  used  in  the  Bessemer  process. 


IROX  AND  STEEL  97 

The  open-hearth  process  was  developed  along  the  lines  of  the 
puddling  process  for  making  wrought  iron,  and  was  made  successful 
only  after  an  improvement  in  the  furnace  used  and  after  a  modifi- 
cation of  some  of  the  steps  in  the  puddling  process.  The  two  ob- 
stacles which  had  to  be  overcome  in  perfecting  the  open-hearth 
process  were  (1)  supplying  suitable  fuel  and  burning  it  in  such  a 
way  that  higher  temperature  could  be  maintained  than  in  the 
puddling  furnace,  and  (2)  building  a  furnace  capable  of  resisting 
this  high  heat  and  serving  the  practical  needs  of  the  process.  It 
was  found  that  in  burning  out  all  the  carbon  and  other  impurities 
a  much  higher  heat  was  necessary  in  order  to  maintain  the  purified 
iron  in  a  molten  state  and  not  let  it  "  come  to  nature  "  in  a  pasty 
condition,  as  in  the  puddling  process. 

To  supply  higher  heat,  the  manufacture  of  producer  gas  was  de- 
veloped, and  the  principle  of  the  regenerative  stove,  as  used  with 
the  blast  furnace,  was  applied  to  the  steel  furnace.  A  better  fur- 
nace, to  withstand  the  heat,'  was  obtained  principally  by  a  careful 
selection  of  pure  refractory  materials  and  by  a  skillful  mixing  and 
burning  of  these  into  high-grade  refractory  bricks. 

The  open-hearth  process  includes  both  the  Siemens  process,  which 
ures  iron  ore  to  assist  in  decarbonizing  the  pig  iron,  and  the  Martin 
process  which  melts  scrap  steel  with  pig  to  dilute  the  impurities  in 
the  latter.  The  combination  of  these  two  is  the  Siemens-Martin 
process,  but  their  individual  distinctions  are  now  lost  sight  of  as 
all  their  combinations  are  included  in  the  one  designation  of  open 
hearth. 

The  composition  of  available  iron  ores  from  different  deposits  of 
the  earth  renders  necessary  the  use  of  both  the  acid  and  the  basic 
methods  in  open-hearth  steel  making,  and  the  control  now  possible 
of  the  various  steps  of  this  process,  particularly  in  the  removal  of 
impurities,  renders  the  product  thoroughly  reliable  as  a  mild  steel 
for  high  grade  uses. 

120.  The  Open-Hearth  Furnace. — This  is  a  reverberatory  furnace 
to  which  is  connected  a  regenerative  system  of  heating.  A  longi- 
tudinal section  of  a  furnace,  lined  for  the  basic  process,  is  shown  in 
Fig.  26,  and  the  diagram  below  the  furnace  is  a  simplified  arrange- 
ment to  show  plainly  the  connections  and  passages  for  air  and  fuel 
gas  in  the  regenerative  system. 


98 


MECHANICAL  PROCESSES 


FIG.  26. — Open-Hearth   Steel-Furnace. 

The  hearth  or  basin,  built  on  flat  steel  plates  FF  which  are 
supported  by  /-beams,  is  composed  of  brick  and  magnesite  as  shown. 
The  charging  doors  D  are  on  the  side  of  the  furnace  next  to  the 
charging  platform  (about  12  feet  above  ground  level)  and  the 
tapping  hole  is  on  the  opposite  side  of  the  furnace.  The  roof  of 
the  furnace  is  made  of  silica  bricks  arched  across  the  furnace. 

The  lower  sides  of  the  air  ports  RE'  and  the  gas  ports  GGf  are 
covered  with  a  layer  of  chrome  brick,  a  basic  material,  as  these 
bricks  may  become  loosened  and  fall  into  the  metal  in  the  hearth. 
Above  the  level  of  the  molten  charge,  where  no  chemical  reaction 
will  result,  the  furnace  is  built  of  silica  bricks  to  save  expense  of 
basic  materials. 


IRON  AND  STEEL  99 

Opening  into  each  end  of  the  furnace  are  two  ports  (R  and  0 
on  one  side  and  R'G'  on  the  other)  which  convey  air  and  fuel  gas 
into  the  space  above  the  charge  where  they  mix  and  the  gas  burns, 
causing  a  long  flame  of  intense  heat  which  sweeps  across  the  length 
of  the  basin  or  hearth.  The  regenerative  system  operates  as  follows  : 
A  supply  of  producer  or  natural  gas  from  the  gas  main,  marked 
in  the  diagram,  passes  along  the  conduit  A,  through  the  highly 
heated  checker-brick  work  in  the  gas  regenerator  G,  and  enters  the 
furnace  through  the  port  G.  Air  drawn  from  the  atmosphere  passes 
through  the  air  inlet,  along  the  conduit  B,  through  the  checker- 
brick  work  of  the  air  regenerator,  and  enters  the  furnace  by  its 
port  R.  Both  gas  and  air  are  highly  heated  by  passing  through  the 
incandescent  checker-brick  work  of  their  respective  regenerators, 
and  as  soon  as  they  come  into  contact  they  unite  in  a  flame  of  in- 
tense heat.  The  draft  of  the  chimney  causes  the  products  of  com- 
bustion to  pass  into  the  gas  and  air  ports  Gr.  and  R'  at  the  opposite 
end  of  the  furnace,  through  the  two  regenerators  below  (to  which 
they  give  up  much  heat)  and  along  the  conduits  K  and  L  into  the 
culvert  T  which  leads  into  a  tall  chimney. 

At  intervals  of  about  half  an  hour,  the  valves  M  and  N  are  re- 
versed, this  causing  a  reversal  of  the  path  of  air  and  gas  through 
the  furnace  and  regenerative  systems.  In  this  way  the  regenerators 
at  the  opposite  ends  of  the  furnace  act  alternately  as  heaters  of 
gas  and  air  as  they  pass  to  the  furnace,  and  absorbers  of  heat  from 
the  burned  gases  after  they  leave  the  furnace.  This  system  makes 
possible  the  maintenance  of  the  high  heat  which  the  open-hearth 
process  requires. 

The  hearth  is  so  supported  as  to  leave  a  large  space  underneath 
open  to  the  air.  This  allows  a  radiation  of  heat  and  prevents  over- 
heating of  the  materials  composing  the  hearth.  The  entire  brick 
work  of  the  furnace  is  rigidly  braced  by  vertical  steel  beams  joined 
above  and  below  the  brick  work  by  tie  rods  as  shown  in  Fig.  27. 

121.  Charging  the  Open-Hearth  Furnace. — The  capacity  of  the 
average  open-hearth  furnace  is  about  60  tons  of  metal. 

Supposing  the  furnace  to  be  at  a  moderate  heat,  ready  for  the 
charge,  the  tapping  hole,  which  leads  from  the  lowest  part  of  the 
basin  through  the  far  side  of  the  furnace,  is  stopped  by  ramming 
into  it  a  quantity  of  magnesite  from  the  outside. 


100  MECHANICAL  PROCESSES 

The  charge  consists  of  pig  iron,  limestone,  usually  iron  oxide, 
and  steel  scrap  if  any  of  this  is  available.  A  quantity  of  limestone, 
determined  by  experience,  is  first  thrown  in  through  the  charging 
door.  The  pig  iron  is  then  brought  molten  in  a  large  ladle  from  the 
mixer  or  directly  from  the  blast  furnace,  and  is  transferred  from 
the  ladle  to  the  furnace  hearth  by  means  of  a  portable  refractory- 
lined  trough.  Sometimes  solid  pigs  may  be  thrown  in  at  the  charg- 
ing door,  but  this  is  not  the  best  practice,  as  there  is  considerable 
saving  of  fuel  and  handling  by  using  molten  pig.  A  quantity  of 
steel  scrap  is  next  thrown  in  if  available,  but  scrap  must  not  be 
used  unless  its  composition  is  known  to  be  suitable  to  the  grade  of 
steel  to  be  made.  Steel  scrap  of  the  proper  composition  is  highly 
desirable,  as  its  impurities  have  been  greatly  reduced  in  its  manu- 
facture. A  small  quantity  of  iron  ore,  low  in  sulphur  and  phos- 
phorus, is  added  to  the  charge. 

122.  Operation  of  the  Open-Hearth  Furnace. — The  purpose  of 
this  operation  is  to  remove,  so  far  as  can  be  done  by  the  process,  the 
silicon,  manganese,  carbon,  phosphorus  and  sulphur  in  the  charge. 
The  removal  of  sulphur  is  difficult  and  uncertain,  phosphorus  is  re- 
moved only  in  the  basic  process,  and  the  remaining  ingredients  are 
usually  reduced  below  the  quantities  desired  in  the  finished  steel 
and  are  re-introduced  at  the  end  of  the  process. 

The  doors  are  tightly  closed  after  charging  and  the  heat  is  regu- 
lated to  melt  the  whole  charge  gradually,  requiring  from  2  to  4 
hours.  The  furnace  temperature  begins  at  once  to  rise,  and  the  lime- 
stone (CaC03)  begins  to  decompose,  forming  CaO  and  C02.  The 
increase  of  heat  soon  causes  the  silicon,  manganese  and  carbon  to 
begin  to  oxidize.  The  oxygen  for  this  purpose  is  supplied  mainly 
from  the  iron  ore  in  the  charge,  to  a  less  extent  from  the  C02  of  the 
lime,  and  to  a  small  extent  from  the  air  entering  through  the  re- 
generators. As  the  charge  becomes  more  and  more  fluid,  the  iron 
and  scrap  become  mixed,  distributing  their  impurities  evenly 
throughout  their  combined  mass.  The  lime  (CaO)  and  iron  oxide 
float  to  the  surface  of  the  molten  iron  and  become  fused,  mixing  with 
the  slag  which  has  begun  to  form  from  the  oxidized  silicon  and  man- 
ganese and  from  the  earthy  matter  of  the  charge.  The  slag  spreads 
out  evenly  over  the  bath  of  iron,  protecting  it  from  the  oxidizing 
action  of  the  flame. 


IRON  AND  STEEL  101 

Unlike  puddling,  no  stirring  or  rabbling  is  done,  though  the 
bottom  of  the  basin  is  raked  over  by  a  long  iron  bar  inserted 
through  the  small  openings  in  the  charging  doors  to  loosen  any  part 
of  the  charge  which  may  have  stuck  to  the  hearth. 

From  the  time  the  metal  is  thoroughly  melted,  samples  are 
occasionally  dipped  from  the  bath  by  means  of  a  small  ladle  with  a 
long  handle.  These  samples  are  cast  in  a  small  iron  mould  kept 
my  the  melter,  and  when  cold,  are  taken  from  the  mould  and 
broken.  The  melter  judges  instantly  by  inspection  of  the  fracture 
the  amount  of  carbon  and  phosphorus  contained,  and  regulates  the 
process  accordingly.  Another  practice,  more  reliable,  is  to  take  the 
sample,  after  it  has  been  cast  and  cooled,  to  the  laboratory  nearby 
and  determine  the  quantity  of  these  elements  by  exact  chemical 
methods,  requiring  15  or  20  minutes. 

As  the  silicon  and  manganese  decrease  in  the  metal,  the  oxidation 
of  carbon  increases,  causing  the  charge  to  '  boil  "  as  in  wrought-iron 
making,  due  to  the  formation  and  escape  of  CO. 

The  melter  watches  the  progress  of  the  operation  through  peep 
holes  in  the  furnace  doors,  protecting  his  eyes  with  dark-colored 
glasses.  His  experience  enables  him  to  regulate  the  furnace  tem- 
perature to  suit  requirements.  He  must  so  reduce  the  temperature 
that  carbon  will  be  burned  out  last.  If  the  carbon  is  burning  too  fast, 
it  is  necessary  to  "  pig  up  "  the  charge  by  adding  solid  pig  to  in- 
crease the  carbon  and  chill  the  bath.  If  phosphorus  (the  last 
element  to  be  attacked)  is  going  too  fast,  as  compared  with  the 
carbon,  as  shown  by  the  sampling,  the  consumption  of  carbon  may 
be  hastened  by  "  oreing  down,"  that  is  by  adding  iron  to  supply 
oxygen  to  consume  the  carbon.  It  is  essential  that  an  excess  of 
iron  oxide  should  not  be  added,  particularly  toward  the  end  of  the 
process,  as  an  undue  amount  of  iron  oxide  cannot  be  carried  by  the 
slag,  and,  at  the  end  of  the  process,  distributes  itself  throughout  the 
steel,  greatly  impairing  its  quality. 

Toward  the  last  of  the  process  when  the  heat  is  still  intense,  and 
the  bath  is  comparatively  quiet  from  the  cessation  of  other  chemical 
action,  the  phosphorus  is  removed  by  becoming  oxidized  and  at 
once  combining  with  lime  to  form  a  stable  compound.  This  com- 
pound, phosphate  of  lime,  enters  the  slag.  The  burning  out  of  the 
carbon  continues  at  varying  rates  throughout  the  entire  operation, 


102  MECHANICAL  PROCESSES 

and  the  last  of  it  is  not  burned  out  until  after  the  removal  of  the 
phosphorus. 

When  the  carbon  has  been,  burned  out,  the  purified  metal  has  a 
higher  melting  point  than  before,  and  would  "  come  to  nature/7  or 
collect  in  plastic  masses  as  in  wrought-iron  making  were  it  not  for 
the  high  heat  of  the  furnace  to  keep  it  thoroughly  fluid. 

In  making  high-carbon  steel  it  is  the  practice  to  stop  the  process 
when  the  carbon  has  burned  out  to  just  below  the  per  cent  desired 
in  the  steel,  and  the  small  quantity  needed  is  introduced  by  re- 
carburizing  as  in  the  Bessemer  process. 

The  elimination  of  sulphur  is  very  irregular.  It  is  safest  to  use 
iron  for  the  charge  which  has  a  sulphur  content  below  that  allow- 
able in  the  steel,  but  this  is  not  always  practicable.  Some  sulphur 
will  unite  with  lime  and  enter  the  slag,  if  very  fluid,  a  condition 
assisted  by  throwing  into  the  furnace  a  quantity  of  fluor-spar.  Man- 
ganese ore  added  to  the  charge  causes  the  formation  of  manganese 
sulphide,  which  also  enters  the  slag. 

The  melter  judges  by  the  appearances  in  the  furnace  and  particu- 
larly by  the  sampling,  when  the  heat  is  finished. 

123.  Tapping  Out. — It  requires  from  6  to  9  hours  to  bring  a 
charge  to  the  condition  for  tapping  out.  In  this  condition  the  bath 
of  slag-covered  metal  contains  some  iron  oxide  and  more  or  less 
oxygen,  carbon  monoxide,  or  other  gases  absorbed  during  the,  process. 
These  must  be  removed  so  far  as  can  be  done,  and  the  metal  must 
be  re-carburized  to  give  it  the  quantity  of  carbon  needed  to  make 
the  grade  of  steel  desired.  In  the  basic  process,  the  materials  used 
to  accomplish  these  results  cannot  be  placed  in  the  furnace  in  pres- 
ence of  the  basic  slag  as  they  will  reduce  the  phosphorus  from  the 
slag  and  cause  it  to  re-enter  the  metal,  therefore  these  materials  are 
mixed  with  the  metal  after  it  is  tapped  from  the  furnace. 

The  best  material  for  this  use  is  ferro-manganese,  as  used  in  the 
Bessemer  process.  Calculation  and  experience  determine  the 
amounts  of  carbon  and  manganese  needed  for  each  furnace  charge 
and  the  quantity  of  "ferro"  necessary  to  give  these  amounts  is 
heated  and  thrown  into  the  metal  as  it  flows  into  the  ladle. 

In  some  cases,  the  metal  charge  may  be  re-carburized  by  throwing 
pig  iron  into  the  furnace.  Still  another  method  of  re-carburizing 
is  to  throw  into  the  ladle  the  necessary  quantity  of  pure  coke  or 


IRON  AND  STEEL 


103 


104 


MECHANICAL  PROCESSES 


coal  ground  fine  and  held  in  paper  bags,  or  a  better  way  of  dis- 
tributing this  form  of  carbon  is  to  allow  it  to  run  into  the  ladle,  as 
the  metal  runs  in,  from  a  hopper  suspended  above  the  ladle.  Con- 
siderable experience  is  needed  in  using  powdered  carbon,  to  intro- 
duce the  correct  quantity,  as  some  of  it  burns  before  it  can  be 
absorbed  by  the  steel. 

The  manganese  in  the  re-carburizer  decomposes  iron  oxide,  takes 
up  oxygen  in  the  metal,  forming  MnO,  which  floats  to  the  surface 
as  slag.  Its  action  assists  mechanically  in  removing  some  of  the 
other  gases  and  some  of  the  slag  in  the  metal. 

Preliminary  to  tapping  out,  a  heated  ladle  large  enough  to  re- 
ceive the  entire  contents  of  the  furnace  is  placed  under  the  tapping 
spout.  The  view  in  Fig.  27  shows  several  large  ladles  along  a  cast- 
ing pit  adjacent  to  a  row  of  iron-bound  brick  furnaces  on  the  right. 
Fig.  28  shows  the  cross  section  of  a  large  steel-cased  ladle  lined 


FIG.  28. — Bottom-Poured  Steel  Ladle. 

with  basic  refractory  material.  This  ladle  is  poured,  or  teemed, 
from  the  bottom  as  shown  in  Fig.  25.  The  bottom  opening  is  con- 
trolled by  a  rod  A,  protected  by  refractory  brick  sleeves  inside  of 
the  ladle.  The  rod  is  manipulated  by  the  handle  II  held  in  suitable 
guides  on  the  side  of  the  shell. 


IRON  AXD  STEEL  105 

A  long  steel  bar  is  used  to  dig  out  the  magnesite  in  the  tapping 
hole.  The  metal  flows  into  the  ladle  and  nearly  fills  it.  The  slag 
flows  from  the  furnace  after  the  metal  has  flowed  out,  filling  the 
ladle  completely.  Much  of  the  slag  runs  over  the  edge  of  the  ladle 
into  a  pit  below,  where  it  cools  and  is  later  lifted  out  by  large 
hooks  attached  to  the  crane. 

124.  Pouring  the  Moulds. — When  all  the  slag  has  flowed  from 
the  furnace,  the  crane  lifts  the  ladle  and  carries  it  while  the  steel 
is  teemed  into  the  moulds,  just  as  shown  in  Fig.  25.    Small  pieces  of 
aluminum  are  thrown  into  each  mould  with  the  steel,  reducing  a  part 
of  any  remaining  iron  oxide  it  may  contain.     The  aluminum  also 
assists  further  to  remove  gases,  which  would  cause  blowholes  in  the 
steel. 

The  ground  space  adjacent  to  the  row  of  furnaces  on  the  tapping 
side  is  called  the  "  casting  pit."  A  long  narrow  pit  is  usually  dug 
for  holding  the  tall  moulds  in  order  that  the  workmen  may  remain 
at  the  ground  level  when  performing  their  work  during  pouring. 

125.  The  Talbot  Process. — This  is  a  continuous  open-hearth  proc- 
ess, and  seems  destined  to  fill  an  important  place  in  steel  produc- 
tion.   The  furnace  used  embodies  the  same  principle  as  the  ordinary 
open-hearth  furnace,  but  it  is  mounted  on  rockers  so  that  any 
quantity  of  metal  or  slag  may  be  poured  out  at  will.     Slag  is 
poured  from  the  charging  side  of  the  furnace  and  metal  from  the 
side  opposite.    When  the  charge  is  ready  for  tapping  out,  a  part  of 
the  slag  is  first  poured  off  and  then  only  about  one-third  of  the 
metal  is  poured  out.     That  part  of  the  charge  which  remains  in 
the  furnace  is  replenished  with  new  stock  to  replace  that  poured 
out.     In  this  way  the  process  is  continued  from  day  to  day,  al- 
though it  is  necessary  to  empty  the  furnace  about  once  a  week  for 
repairs  to  the  hearth  and  the  lining. 

To  the  charge  remaining  in  the  furnace  after  each  pour,  there  is 
added  mill  scale  or  ore,  and  limestone.  These  form  a  highly  basic 
and  a  highly  oxidizing  slag,  and  when  these  materials  are  thoroughly 
fused,  a  quantity  of  molten  pig  iron  is  slowly  poured  into  the  fur- 
nace from  the  ladle.  As  this  metal  passes  through  the  slag,  a  very 
vigorous  reaction  takes  place  between  the  iron  oxide  and  the  im- 
purities in  the  metal,  thus  quickly  burning  out  a  large  percentage 
of  these  impurities  and  thereby  shortening  the  process. 


106  MECHANICAL  PROCESSES 

The  advantages  of  this  process  are  as  follows,  viz. : 

(1)  A  wider  range  is  made  possible  in  the  grade  of  pig  iron 
which  can  be  used. 

(2)  The  process  is  not  dependent  on  steel  scrap,  which  may  be 
difficult  to  obtain. 

(3)  The  wear  and  tear  on  the  furnace  hearth  and  lining  are 
much  reduced. 

(4)  A  greater  output  of  steel  is  obtained  in  a  given  time. 

A  tilting  furnace,  used  in  this  process,  has  a  capacity  of  200  tons 
or  slightly  more. 

126.  The  Duplex  Process. — This  is  merely  a  combination  of  the 
Bessemer  and  open-hearth  processes. 

Pig  metal  is  blown  in  an  acid  Bessemer  converter  until  silicon, 
manganese,  and  part  or  all  of  the  carbon  are  removed.  It  is  then 
practically  a  molten  steel  high  in  phosphorus.  From  the  converter 
it  is  conveyed  to  the  basic  open-hearth  furnace  for  refining,  for  re- 
moval of  the  phosphorus,  and  for  re-carburization. 

The  advantage  claimed  for  this  process  is  that  it  saves  time, 
brings  less  wear  and  tear  on  the  open-hearth  furnace  (which  is  the 
expensive  furnace  in  steel  making),  and  gives  a  better  product  than 
by  the  open-hearth  process  alone.  It  combines  the  acid  process  of 
the  converter  with  the  basic  process  of  the  furnace. 

127.  Uses   of   Open-Hearth   Steel. — Open-hearth   steel   combines 
the  two  requisites  of  (1)  a  very  reliable  steel  made  in  large  quanti- 
ties, and   (2)   moderate  cost  of  production.     Steel  made  by  this 
process  is  used  for  bridge  material,  ship  plates  and  frames,  axles, 
tires,  springs,  wire,  steel  castings  and  tools  not  requiring  extremely 
hard-cutting  edges. 

Armor  plate,  common  projectiles,  gun  forgings  and  boiler 
material  are  made  of  open-hearth  steel  from  selected  materials 
especially  treated  to  insure  a  minimum  of  phosphorus  in  the  steel. 

High-carbon  steel  can  be  made  by  the  open-hearth  process,  but 
there  is  difficulty  in  eliminating  sulphur  and  phosphorus.  Because 
of  this  condition,  high-carbon  steel  is  made  mostly  by  the  crucible 
process,  in  which  the  impurities  can  be  carefully  regulated. 


IRON  AND  STEEL  107 

The  amount  of  phosphorus  in  iron  ore  determines  whether  the 
>acid  or  the  basic  process  must  be  used  in  making  steel  from  the 
iron  smelted  from  this  ore.  The  basic  process  is  the  one  used  to 
reduce  phosphorus  down  to  safe  limits,  but  there  is  always  the  risk 
that  phosphorus  may  by  some  accident  get  back  from  the  slag  into 
the  steel  before  tapping  out. 

128.  The  Crucible  Process.— The  method  of  melting  steel  in 
crucibles  or  pots  was  brought  into  use  as  a  means  of  improving  the 
product  of  the  cementation  furnace,  as  mentioned  in  Par.  113. 
The  introduction  of  the  Bessemer  and  the  open-hearth  steel-making 
processes  left  very  limited  need  for  the  product  of  the  cementation 
furnace,  but  the  method  of  purifying  steel  and  iron  scrap  by  melt- 
ing it  in  the  crucible  gave  a  means  of  producing  a  higher  quality 
of  steel  than  could  be  supplied  by  other  processes.  The  crucible 
melting  feature  of  the  cementation  process  was  therefore  retained 
and  turned  to  excellent  use.  The  expense  of  the  crucible  process 
(about  three  times  that  of  the  open-hearth  process)  would  soon 
cause  the  disuse  of  crucible-made  steel  if  the  steel  made  by  other 
processes  could  be  substituted  for  it. 

The  ingredients  in  crucible  steel  can  be  regulated  as  desired, 
giving  full  control  of  the  kind  of  product  turned  out,  and  making 
possible  the  manufacture  of  many  alloy  steels  containing  small 
quantities  of  unusual  ingredients  which  would  not  bring  dependable 
results  by  the  Bessemer  and  open-hearth  methods. 

The  crucible  method  is  in  many  cases  a  method  of  steel  refining 
rather  than  one  of  steel  making. 

The  method  of  manufacture — melting  in  small  pots  containing 
about  100  Ibs. — makes  the  crucible-steel  output  very  small  when 
compared  with  Bessemer  and  open-hearth  outputs,  and  the  product 
is  disposed  of  entirely  in  making  metal-cutting  tools,  wood-working 
tools,  piano  and  other  wires  of  high  quality,  highly  tempered 
springs,  armor-piercing  projectiles  and  other  steel  articles  demand- 
ing exceptional  purity  or  hardness.  Crucible  steel  is  sometimes 
designated  as  cast  steel,  or  crucible  cast  steel,  because  it  may  be  cast 
into  various  shapes  by  pouring  from  the  crucible  into  suitable 
moulds,  and  it  is  the  first  method  by  which  steel  castings  were  made. 


108  MECHANICAL  PROCESSES 

129.  Materials  used  in  Crucible  Steel. — Crucible  steel  is  made 
principally  from  steel  scrap,  with  which  is  combined  cast  iron  if 
the  carbon  is  to  be  increased,  or  muck  bar  if  the  carbon  is  to  be 
lowered.  All  of  these  materials  are  of  known  chemical  composition 
and  are  selected  for  their  purity. 

In  the  central  space  of  the  building  devoted  to  this  process  is 
usually  placed  the  set  of  crucible-steel  furnaces,  and  along  the  walls 
on  one  or  two  sides  are  placed  a  number  of  bins  not  unlike  horse 
stalls  in  a  barn.  In  these  bins  are  stored  scraps  or  punchings  of 
steel,  pieces  of  muck  bar,  and  chunks  of  pig  iron,  all  cut  or  broken 
small  enough  to  be  readily  packed  in  the  crucibles.  A  highly  im- 
portant feature  of  these  bins  is  that  great  care  is  taken  not  to  let 
any  metal  be  placed  in  them  until  samples  are  chemically  analyzed 
and  found  suitable  as  crucible  steel  material;  also  each  bin  is  re- 
served strictly  for  scrap  of  but  one  composition.  It  is  essential 
that  there  be  received  no  scrap  which  contains  a  greater  per  cent 
of  sulphur  or  phosphorus  than  is  admissible  in  the  finished  steel, 
because  there  is  no  practical  way  of  removing  these  impurities  in 
this  process.  It  is  a  common  saying  in  crucible-steel  making  that 
everything  which  goes  into  the  pot  comes  out,  meaning  that  none 
of  the  ingredients  of  the  charge  are  lost  by  either  an  oxidizing  or  a 
reducing  action  of  the  furnace  flame  as  in  the  other  processes. 

The  materials  for  the  highest  grade  of  this  steel  are  usually  of 
Swedish  or  other  iron  exceptionally  pure.  These  materials  are  in 
the  forms  of  muck  bar  and  pig  iron  mixed  to  give  the  per  cent  of 
carbon  required  in  the  finished  steel.  Wrought  iron  (muck  bar) 
may  be  melted  with  enough  charcoal  in  the  pot  to  bring  it  up  to 
the  degree  of  carbon  required,  or  cast  iron  may  be  mixed  with  a 
little  good  scrap  to  lower  the  carbon. 

Other  materials  more  or  less  needed  in  making  up  a  crucible 
charge  are  ( 1 )  charcoal  free  from  sulphur  for  carburizing  the  steel ; 
(2)  ferro-manganese  for  reducing  any  iron  oxide  in  the  scrap  of 
the  charge  (usually  stirred  in  just  before  the  crucible  is  taken  from 
the  furnace)  ;  and  (3)  some  form  of  silica  (sand  or  ground  silica 
brick)  to  act  as  a  flux  for  taking  up  slag  and  oxides  melted  from 
the  scrap. 


IRON  AND  STEEL 


109 


130.  Crucibles. — In  America,  crucibles  are  made  of  a  mixture  of 
half  graphite  and  half  fire  clay,  carefully  kneaded,  and  moulded 
compactly  by  hand  to  shape  as  shown  in  Fig.  29.  After  they  are 


FIG.  29. 

moulded,  they  are  allowed  to  dry  for  several  days  or  weeks,  and 
those  not  cracked  or  distorted  in  drying  are  burned  in  a  kiln. 

The  clay  crucible  is  used  in  England,  but  is  not  so  strong  when 
hot  nor  so  durable  as  the  clay  and  graphite  mixture.  However,  for 
low-carbon  and  alloy  steels,  a  graphite  crucible  must  have  an  inside 
lining  of  clay  to  keep  the  graphite  from  being  absorbed  by  the 
molten  steel. 

A  clay  crucible  lasts  only  through  the  two  or  three  heats  of  a 
single  day,  while  the  graphite  crucible,  more  expensive,  lasts  for 
ten  or  twelve  heats  and  is  not  so  easily  broken  in  handling.  The 
bottoms  of  discarded  crucibles  are  sawed  off  to  be  used  as  lids  for 
new  crucibles. 

131.  The  Crucible  Furnace. — Modern  crucible  steel  furnaces  are 
heated  with  natural  or  producer  gas  by  the  regenerative  system, 
though  many  coke-heated  furnaces,  similar  to  a  brass-melting  fur- 
nace, are  still  in  use.  Fig.  30  shows  a  vertical  transverse  section  of 
a  typical  modern  gas  furnace  for  melting  crucible  steel.  The 
greater  part  of  the  structure  is  in  the  regenerators,  their  walls  and 
ports,  while  the  furnace  proper  (the  brick  work  surrounding  the 
crucibles)  occupies  a  comparatively  small  space.  The  regenerators 
have  gas,  air,  and  chimney  connections  as  shown  in  Fig.  26  and 
need  not  be  further  described  here.  The  top  of  the  brick  work  is 
8 


110 


MECHANICAL  PROCESSES 


covered  with  steel  plates  A,  A,  to  form  a  suitable  charging  floor  for 
the  convenience  of  the  furnace  men.  The  structure  contains  usually 
four  or  more  receptacles,  B,  which  are  the  spaces  for  holding  the 
crucibles  and  are  commonly  called  the  "  melting  holes."  Each 
hole  is  large  enough  for  six  crucibles,  and  is  covered  with  three 
movable  lids,  one  of  which  is  marked  C.  Linings  of  melting  holes 
and  of  gas  and  air  ports  are  so  built  of  refractory  brick  that  they 
may  be  easily  renewed  when  worn  out. 


FIG.  30. — Crucible-Steel  Furnace. 

The  several  sets  of  melting  holes  are  separated  by  thick  fire-brick 
partitions.  The  bottom  brick  work  of  the  melting  holes  and 
these  partitions  are  supported  by  ribbed  cast-iron  plates,  D ,  placed 
edge  to  edge  over  the  vault  F,  which  extends  the  entire  length  of 
the  structure.  Each  melting  hole  has  a  7-inch  opening  through  the 
bottom  to  allow  the  steel  to  flow  into  the  vault  in  case  a  crucible 
breaks.  The  vault  F  is  kept  closed  at  the  ends  while  the  furnace 
is  in  use. 

Directly  over  the  line  of  melting  holes  and  enough  above  to  allow 
ample  head  room,  is  a  trolly  bar  equipped  for  lifting  and  lowering 
crucibles.  The  melting-hole  covers  are  usually  dragged  aside  and 
pushed  in  place  again  by  an  iron  rod  suitably  made  for  this  use. 


IRON  AND  STEEL  111 

Crucibles  are  lifted  from  or  lowered  into  the  furnace  by  means  of 
tongs  supported  from  the  trolley  bar. 

132.  Charging  a  Crucible. — A  memorandum  directing  the  sup- 
erintendent of  the  crucible  department  to  make  a  particular  grade 
of  steel  gives  him  the  analysis  of  what  the  steel  must  contain. 

From  the  several  bins  are  selected  such  materials  in  composition 
and  quantity  as  will  average  up  the  composition  required,  and  any 
special  alloy  material  is  introduced  in  the  form  of  a  compound. 
When  each  kind  of  material  has  been  weighed  out  and  piled  by 
itself  on  the  charging  floor,  enough  crucibles  are  set  out  to  hold 
the  entire  charge.  Each  crucible  is  packed  cold  with  its  proportion 
from  each  kind  of  material.  Flux  may  be  put  in  first  or  may  be 
thrown  in  over  the  material  when  packed  in.  A  little  wet  sand  is 
plastered  around  the  top  edge  of  the  crucible,  the  lid  is  put  on,  and 
the  crucible  is  then  lifted  by  the  tongs,  swung  from  the  trolley 
bar  and  lowered  into  the  furnace. 

Crucibles  just  poured  may  be  again  lowered  in  the  furnace  and 
charged  by  aid  of  a  funnel. 

133.  Operation  of  the  Crucible  Furnace. — After  the  regenerators 
have  brought  the  furnace  up  to  a  high  heat,  the  charged  crucibles 
are  lowered  one  by  one  into  the  melting  holes.    The  chimney  draft 
prevents  flame  from  coming  out  of  the  melting-hole  openings  while 
the  crucibles  are  being  lowered  in,  but  these  openings  should  not 
be  left  open  longer  than  absolutely  necessary. 

The  path  of  the  gases  through  the  regenerators  is  changed  about 
every  20  minutes  to  keep  the  crucibles  from  eating  away  on  the  hot 
side.  In  about  an  hour  the  melter  looks  into  the  pots  to  see  if  the 
melting  has  begun,  using  a  pair  of  blue  glasses  framed  in  a  small 
board  to  protect  his  eyes.  His  experience  enables  him  to  make  such 
other  inspections  as  will  keep  him  in  thorough  touch  with  the 
progress  of  melting.  In  from  3  to  6  hours  the  charge  is  thoroughly 
melted.  It  is  slightly  stirred  with  an  iron  rod  to  lift  any  lumps  of 
muck  bar  possibly  at  the  bottom,  and  to  mix  the  charge  thoroughly. 
The  seal  of  the  lid  on  the  crucible  is  broken  by  such  inspections, 
but  a  new  joint  is  soon  made  by  the  heat  of  the  furnace. 

After  becoming  molten,  the  temperature  of  the  metal  will  in- 
crease, and  soon  the  occluded  gases  begin  to  boil  out.  This  step 
lasts  about  20  minutes  and  is  called  a  killing "  or  "  melting  to  a 


112  MECHANICAL  PROCESSES 

dead  heat."  It  requires  skill  to  determine  when  this  has  gone  far 
enough.  At  the  proper  time.,  the  crucible  is  lifted  from  the  furnace 
and  is  set  into  a  holder  shown  in  Fig.  31  to  be  poured  directly  into 
a  small  mould,  or  into  a  hot  ladle  in  which  the  contents  of  several 
crucibles  are  assembled  if  a  large  mould  is  to  be  poured. 

If  a  crucible  is  taken  from  the  furnace  before  the  metal  is  te  dead  " 
it  will  pour  "  fiery/'  throwing  off  sparks  and  showing  some  agita- 
tion due  to  the  escape  of  gasses,  but  if  kept  too  long  in  the  furnace, 
the  metal  will  pour  quietly,  and  the  moulded  insrots  will  be  solid, 
but  will  be  brittle  and  weak.  The  cause  of  this  is  uncertain,  but  is 
possibly  to  the  absorption  of  an  excess  of  silicon  from  the  crucible 
walls  at  a  very  high  heat. 

In  pouring  from  the  crucible  into  the  mould,  which  is  washed 
inside  with  lime-wash  to  prevent  the  steel  from  sticking,  great  care 


FIG.  31. — Ladle  Shanks. 

must  be  exercised  to  keep  the  metal  from  striking  the  side  of  the 
mould  as  this  would  chill  a  film  of  it  and  cause  a  lamination  in  the 
ingot. 

It  requires  a  large  crucible  plant,  expert  skill  and  quick  handling 
to  assemble  enough  crucible  steel  to  make  successfully  a  large  cast- 
ing. The  Krupp  works  in  Germany  make  crucible-steel  ingots  large 
enough  for  high-powered  guns  and  armor  plate. 

134.  Properties  of  Crucible  Steel.— The  reason  for  the  superiority 
of  crucible  steel  over  steel  of  like  composition  from  other  processes 
is  not  always  apparent,  but  is  no  doubt  due  in  greater  part  to  the 
following  conditions,  viz. : 

(1)  The  stock  is  carefully  selected,  and  has  had  the  advantage  of 
more  or  less  refining  by  having  been  previously  produced  in  a  steel- 
making  process. 

(2)  The  covering  of  the  crucible  enables  the  elements  of  the 
charge  to  be  better  controlled  in  melting  by  avoiding  losses  due  to 
the  action  of  the  flame. 

(3)  The  melting  of  the  charge  distributes  the  carbon  and  other 


IRON  AND  STEEL  113 

elements  equally  throughout  the  mass,  and  sets  free  the  slag  and 
oxides  which  the  scrap  metals  contained,  allowing  them  to  float  to 
the  surface. 

(4)  The  boiling  out  of  occluded  gases  before  pouring  gives  a  more 
compact  steel. 

(5)  Before  a  crucible-steel  billet  is  rolled,  it  is  thoroughly  ham- 
mered,, while  hot,  under  a  steam  hammer  to  make  it  compact  and 
dense.    This  is  called  tilting  because  of  the  old  method  of  hammer- 
ing newly  made  iron  under  a  tilting  machine. 

About  the  only  important  chemical  changes  are  (1)  the  reducing 
of  iron  oxide  by  the  introduction  of  ferro,  when  this  is  found  neces- 
sary, and  (2)  the  absorption  of  carbon  by  the  metal.  Incidentally 
the  metal  will  absorb  some  manganese  from  the  charge,  silicon  from 
the  crucible  walls,  and  sulphur  and  phosphorus  from  the  slag,  if 
these  elements  are  present  in  the  crucible. 

135.  Special  Steels. — Iron  will  alloy  with  most  metals,  and  some 
of  these  alloys  have 'been  highly  developed  for  special  purposes. 
These  alloys  are  all  alloys  of  steel  and  a  small  per  cent  of  another 
metal.  The  metals  most  commonly  used  are  nickel,  chromium,  man- 
ganese, vanadium,  and  tungsten,  and  investigations  will  possibly 
develop  some  surprising  results  from  the  use  of  other  metals.  Car- 
bon is  always  present,  but  apparently  as  a  secondary  element. 

These  steels  have  several  names,  as  "  alloy  "  steel,  "  high-speed  " 
steel,  "  self -hardening  "  steel  and  others  assigned  as  commercial  or 
trade  names. 

The  advantages  of  these  alloy  steels  are  numerous,  although  these 
advantages  are  not  embodied  alike  in  all  of  the  different  composi- 
tions. Among  the  advantages  are  increased  hardness,  greater  elastic 
and  tensile  strength,  increased  elongation  before  breaking,  resist- 
ance to  corrosion,  and  retention  of  hardness  under  the  influence  of 
high-friction  heating.  The  most  important  uses  for  alloy  steels 
are  ( 1 )  for  very  hard,  cutting  tools  which  can  stand  heavy  machine 
cutting  with  but  little  wear,  and  (2)  for  high-grade  rolled  or  forged 
structural  material  for  use  where  minimum  weight  and  maximum 
strength  of  material  are  required.  Much  alloy  steel  is  now  used  in 
automobiles. 

Nickel-steel  has  a  very  wide  range  of  use  for  bridge  material, 
ordnance  forgings,  wire  cables,  automobile  parts,  large  axles,  engine 


114  MECHANICAL  PROCESSES 

shafts,  and  moving  parts  of  marine  and  other  high-grade  engines. 
It  contains  from  1.5  to  4.5$  of  nickel,  has  a  high  elastic  limit  and 
the  tensile  strength  is  between  70,000  and  100,000  Ibs.  per  square 
inch,  according  to  treatment,  while  the  best  low-carbon  boiler-plate 
ranges  around  72,000  Ibs.  The  presence  of  nickel  in  steel  greatly 
retards  corrosion. 

Chromium  has  a  more  intense  effect  than  nickel,  in  the  same 
directions.  Chrome  steel  is  used  for  automobile  axles  and  other 
forgings.  Chromium  is  frequently  combined  in  the  alloy  with 
nickel,  and  nickel-chrome  steel  is  used  for  toothed  wheels  requiring 
great  strength  and  resistance  to  wear,  for  very  hard  steel  plates  as 
in  plows  or  burglar-proof  safes,  for  jaws  of  rock  crushers,  and  for 
armor  and  armor-piercing  shells.  Specimens  of  chrome  steel  shows 
an  elastic  strength  of  180,000  Ibs.  and  a  tensile  strength  of 
210,000  Ibs. 

Manganese  steel  possesses  to  a  high  degree  the  rare  combination 
of  extreme  hardness  and  high  ductility  in  one  piece  of  metal.  It 
is  also  non-magnetic.  Its  uses  are  restricted  because  cutting  it  to 
shape  is  extremely  difficult.  It  may  be  forged,  rolled  hot,  or  cast, 
but  any  finishing  of  the  shapes  so  produced  must  be  done  by  grind- 
ing. It  is  used  for  burglar-proof  safes,  rails  for  curves  on  railways, 
jaws  for  rock  crushers,  etc.  Castings  of  manganese  steel  may  be 
battered  badly  out  of  shape  without  breaking,  but  they  are  too  hard 
to  be  machined. 

8  elf -hardening  steel  is  so  named  because  the  steel  hardens  in  the 
air  upon  cooling,  and  does  not  need  to  be  plunged  hot  into  oil  or 
water  as  is  the  case  in  hardening  carbon  steel.  High-speed  steel  is 
so  named  because  when  used  for  machine  tools,  it  can  cut  metal  at 
a  very  rapid  rate  without  losing  its  hardness  or  without  wearing 
away  under  the  friction  and  resistance  of  cutting. 

The  hardest  steel  so  far  recorded  contains  .68$  of  carbon,  3.01$ 
of  chromium,  19.37$  of  tungsten,  and  .04$  of  silicon. 

136.  Ingot  Moulds.  Stripping  Ingots. — The  usual  form  of  ingot 
mould  for  Bessemer  and  open-hearth  steel  is  shown  in  Fig.  32, 
which  shows  three  moulds  sitting  on  a  common  base  of  heavy  cast 
iron  carried  by  an  ingot  car.  Fig.  33  shows  a  longitudinal  cross 
section  of  one  of  these  moulds. 


IRON  AND  STEEL 


115 


FIG.  32. — Ingot  Car. 

n L 


} 


FIG.  33. — Mould  for  Steel  Ingots. 


116 


MECHANICAL  PROCESSES 


The  moulds  are  made  of  cast  iron,  are  open  top  and  bottom,  and 
are  provided  with  suitable  lugs  for  handling.  The  mould  cavity  for 
standard  moulds  is  17%  x  19%  inches  at  the  top,  20i/2  x  22%  at 
the  bottom,  and  about  6  feet  high,  for  a  6500-lb.  ingot.  It  is 
slightly  larger  at  the  bottom  than  at  the  top  to  facilitate  forcing  the 
ingot  out  when  it  has  become  sufficiently  cooled.  The  mould 
corners  are  rounded  to  avoid  forming  laminations  which  would  re- 
sult from  square  corners  when  rolling  the  ingot,  and  to  relieve  the 
ingot  corners  of  a  chilled  and  crystalline  condition  such  as  would 
result  from  the  rapid  cooling  of  sharp  corners  in  the  mould.  The 
walls  of  the  mould  are  about  5  inches  thick,  and  the  weight  is  suffi- 


FIG.  34.— Crucible-Steel  Billet  Moulds. 

cient  to  hold  the  mould  down  firmly  on  its  base  during  the  pouring 
of  the  steel.  A  fin  of  steel  may  run  under  the  lower  edge  of  the 
mould,  but  it  is  thin  enough  to  chill  very  quickly  and  thus  stop 
the  opening. 

The  moulds  shown  are  poured  at  the  top,  but  for  higher-grade 
steel,  a  mould  is  arranged  with  a  long  clay-lined  tube  up  the  side 
so  that  the  metal  may  enter  the  mould  space  from  the  bottom. 

For  crucible  steel,  ingot  moulds  are  much  smaller  and  of  differ- 
ent design  from  the  larger  moulds,  although  the  shape  of  the  ingot 
is  nearly  the  same,  i.  e.,  rounded  corners,  long,  and  sometimes 
tapering.  For  crucible  steel,  Fig.  34  shows  two  views  of  an  ingot 


IRON  AND  STEEL 


117 


mould  made  in  halves,  closed  at  the  bottom  and  held  together  by 
iron  rings  and  wedges. 

The  operation  of  "  stripping  "  a  large  mould,  i.  e.,  removing  the 
ingot  from  it,  is  accomplished  by  a  specially  built  traveling  crane, 
such  as  shown  in  Fig.  35.  A  train  of  ingot  cars  is  run  under  the 
crane  and  the  crane-tongs  T  lift  each  mould  by  the  heavy  lugs  at 
the  top  and  if  the  ingot  does  not  drop  out,  it  is  pressed  out  by  a 
hydraulic  plunger,  K,  rigged  for  this  purpose. 


FIG.  35. — Ingot  Stripper. 

Four  ingots  stripped  from  the  moulds  are  shown  on  the  right  in 
this  view. 

Ingots  for  armor  plates,  large  gun  parts,  and  other  special  forg- 
ings  are  cast  in  very  large  moulds,  specially  shaped  and  sometimes 
lined  inside  with  clay.  Some  ingots  are  cast  in  long  fluted  columns 
for  special  advantages  in  cooling  and  working. 

137.  Impurities  in  Steel.  Segregation. — Besides  carbon,  which 
determines  hardness,  steel  contains  a  trace  or  more  of  manganese, 
silicon,  phosphorus  and  sulphur,  which  came  to  it  from  the  ore,  or 
during  the  various  stages  of  manufacture.  Traces  of  other  metals 


118  MECHANICAL  PROCESSES 

also  come  from  ores,  but  these  are  not  frequent.  In  additin  to  these 
impurities,  almost  all  steels  contains  some  slag  and  oxides  acquired 
during  the  molten  state  in  the  furnace,  and  more  or  less  occluded 
gas  acquired  in  furnace  reactions  or  during  pouring  into  ladle  and 
moulds. 

Skill  and  modern  equipment  in  the  manufacture  of  steel  have 
made  it  possible  to  control  in  a  great  degree  the  quantity  of  im- 
purities in  the  steel,  but  there  is  no  way  to  control  the  distribution 
of  these  impurities  throughout  the  mass  of  the  ingot  while  it  is 
cooling  in  the  ingot  mould.  As  the  ingot  cools,  these  impurities 
tend  to  go  to  the  hottest  part,  which  is  the  center  of  the  mass. 
Through  this  tendency  the  metal  is  not  uniform  in  composition  and 
hence  not  uniform  in  strength  and  quality.  This  concentration  of 
the  impurities  at  the  center  of  the  ingot  is  known  as  segregation. 

After  steel  is  poured  into  the  mould,  and  becomes  quiet,  there  is 
an  effort  of  the  gases,  slag,  oxides,  and  of  some  other  impurities  to 
rise  to  the  top,  as  most  of  them  are  lighter  than  the  metal.  After 
the  ingot  has  cooled  or  after  it  has  been  re-heated  to  be  rolled,  a 
quantity  of  the  impurities  is  eliminated  by  cutting  off  the  upper  end 
of  the  ingot  before  it  is  used.  This  is  called  the  discard  or  crop  end, 
and  is  frequently  as  much  as  30^  of  the  whole  ingot.  A  discard  of 
from  3  to  6^  is  frequently  made  from  the  bottom  end  of  an  ingot. 
Steel  for  uses  not  particularly  requiring  strength  may  have  little 
or  no  discard  cut  from  the  ingot. 

138.  Defects  in  Steel  Ingots. — Besides  the  presence  of  gas  bubbles, 
and  the  result  of  segregation  in  a  steel  ingot,  there  are  other  defects 
which  result  from  the  pouring  and  cooling  of  the  ingot  in  the 
mould. 

A  mass  of  molten  metal  naturally  begins  to  cool  at  the  surface, 
and  as  this  chills,  it  forms  a  solid  envelope  about  the  molten  mass 
in  the  interior.  The  contraction  which  results  from  cooling  causes 
the  metal  to  be  drawn  to  the  solid  part  as  it  cools,  and  in  this  way 
the  central  part  of  the  ingot  finally  cools  in  a  honey-combed  state. 
The  formation  of  the  cavity  at  the  center  of  the  ingot  is  called 
piping.  By  the  action  of  gravity  on  the  molten  metal  this  cavity 
is  formed  well  toward  the  upper  end  of  the  ingot,  and  for  this 


IRON  AND  STEEL  119 

reason,  the  ingot  is  always  cast  on  end.  The  piping  should  be  cut 
off  in  the  discard. 

Surface  cracks  will  appear  if  the  ingot  is  taken  hot  from  the  mould 
and  exposed  to  air  sufficiently  cold  to  make  this  surface  contract 
enough  to  disrupt.  These  cracks  may  ruin  steel  otherwise  good,  be- 
cause in  rolling  the  ingot,  cracks  simply  close  up  but  do  not  weld 
together,  and  in  this  way  the  material  is  more  or  less  weakened. 

In  pouring,  globules  of  steel  are  apt  to  splash  against  the  sides 
of  the  mould  and  become  chilled  into  shot.  These  fall  into  the 
molten  metal  but  may  not  be  wholly  re-melted,  particularly  if  they 
rest  against  the  sides  of  the  mould.  When  the  ingot  solidifies  these 
shot  are  more  or  less  separate  from  the  metal  surrounding  them. 
These  defects  are  called  cold-shuts. 

Also  in  pouring,  a  film  of  metal  from  the  ladle  may  strike  on  the 
inside  of  the  mould  and  become  chilled,  sticking  to  the  mould.  This 
forms  a  lamination,  as  molten  metal  rising  in  the  mould  does  not 
entirely  re-melt  it. 

139.  Fluid  Compressed  Steel. — Many  efforts  have  been  made  to 
improve  open-hearth  and  Bessemer  steels,  with  the  view  to  having 
them  approach  crucible  steel  in  quality  without  having  its  high 
cost  of  production. 

One  of  the  methods  used  for  improving  open-hearth  steel  is 
known  as  the  Whitworth  process  of  fluid  compression.  This  con- 
sists of  applying  to  a  mass  of  molten  steel  which  has  been  poured 
from  the  ladle  into  a  suitably  shaped  mould,  a  pressure  varying 
from  2500  to  4000  Ibs.  per  square  inch. 

This  process  is  of  benefit  because  the  reliability  of  steel  is  in- 
creased if  (1)  the  density  of  the  mass  is  increased,  and  (2)  if  the 
mass  is  made  homogeneous,  i.  e.,  the  composition  is  the  same 
throughout  the  mass.  It  is  unlikely  that  this  process  increases  the 
density  of  the  steel  itself,  but  it  does  decrease  greatly  the  size  of  the 
gas  bubbles  in  the  steel,  and  compresses  the  particles  of  slag  into 
compact  masses.  Piping  is  lessened  but  not  prevented  by  this 
process,  and  possibly  segregation  is  lessened.  The  steel  under 
pressure  is  longer  in  solidifying,  which  gives  the  gas,  slag,  and 
oxides  more  time  to  rise  into  the  discarded  part  of  the  ingot. 


120 


MECHANICAL  PROCESSES 


140.  Compressing  Steel. — The  method  of  compressing  steel  is 
briefly  as  follows :  On  a  specially  built  car  not  unlike  an  ingot  car 
is  placed  a  large  cylindrical  mould  built  up  of  very  heavy  cast-iron 
sections,  one  of  which  is  shown  in  Fig.  36,  bolted  by  their  end 
flanges  to  each  other  and  to  a  cast-iron  bottom.  For  very  .heavy 
pressures,  however,  a  steel  tube  forms  the  length  of  the  mould,  and 
this  is  fortified  by  a  series  of  short  steel  tubes  slipped  over  the  long 


Ef7T| 


i  ;v 


FIG.  36. — Mould  Section  for  Whitworth  Press. 

tube,  as  shown  in  Fig.  37.  The  inside  diameter  of  the  mould  is 
about  42  inches  and  its  depth  about  16  feet.  The  inside  of  the 
mould  is  lined  with  cast-iron  bars  as  shown  at  A  A  in  Fig.  36, 
plastered  over  with  about  %  inch  of  loam,  a  refractory  mixture  of 
sand  and  clay.  Two  edges  of  each  of  the  bars  are  champfered  to 
form  vertical  openings,  as  at  BB,  by  which  air  in  the  loam  and  some 
gases  in  the  metal  may  escape. 

The  inside  of  the  mould,  having  been  thoroughly  dried  and 
heated  very  hot  by  a  charcoal  or  oil  fire,  is  poured  nearly  full  of 
steel  tapped  from  the  furnace.  The  car  is  then  run  under  a  hydrau- 


IRON  AND  STEEL 


121 


lie  press  (Fig.  37),  the  upper  head  D  of  which  is  stationary  and 
carries  a  heavy  plug  E  which  will  exactly  fill  the  upper  end  of  the 
open  mould.  The  car  having  been  correctly  placed,  the  hydraulic 
ram  P  lifts  the  car  body  and  the  mould  until  the  plug  E  is  pressed 
to  the  intensity  desired  against  the  surface  of  the  molten  steel.  A 


FIG.  37. — Whitworth  Press  for  Molten  Steel. 

film  of  metal  squeezes  up  between  E  and  the  mould  lining,  but  it 
soon  solidifies  and  prevents  the  escape  of  more  metal.  The  pressure 
is  held  on  the  steel  for  about  four  hours,  until  the  ingot  has  solidified. 
Some  gas  and  slag  are  pressed  out  at  the  top  and  also  from  the 
surface  of  the  metal  in  contact  with  the  mould,  but  pressure  cannot 
squeeze  anything  from  the  interior  of  the  molten  mass.  However, 
it  reduces  the  size  of  the  bubbles  and  compresses  the  slag  particles 


122  MECHANICAL  PROCESSES 

densely  together  in  the  interior  of  the  mass.  An  ingot  fifteen  feet 
long  is  decreased  about  12  or  14  inches  in  length  by  this  pressure. 
From  20  to  30%  is  cut  from  the  top  of  this  ingot,,  after  it  is  cold,  as 
a  discard. 

Steel  of  this  kind  is  used  for  guns,  armor,  and  marine-engine 
shafting.  Its  uses  are  not  extensive  because  the  expensive  equip- 
ment for  making  it  add  to  its  cost  and  thus  prevents  a  great  de- 
mand for  this  steel  in  preference  to  other  grades.  The  Whitworth 
process  is  not  applied  to  Bessemer  steel  because  open-hearth  steel 
has  the  preference  as  a  better  product  to  begin  with. 

141.  The  Electric  Refining  Furnace. — Another  method  of  im- 
proving the  quality  of  steel,  recently  perfected,  is  that  of  electric 
refining.  This  method  seems  destined  for  a  wide  range  of  useful- 
ness in  steel  making,  as  it  does  more  than  the  Bessemer  or  open- 
hearth  methods  can  do  in  eliminating  initial  impurities  and  in  turn- 
ing out  a  product  freer  from  slag,  oxides  and  gases.  In  fact  the 
electric  furnace  promises  to  rival  the  crucible  furnace  in  quality  of 
product  at  lower  cost. 

The  ability  of  the  electric  furnace  to  eliminate  sulphur  and 
phosphorus  brings  into  the  range  of  practical  usefulness  the  enor- 
mous deposits  of  iron  ores  which  have  heretofore  been  excluded  be- 
cause none  of  the  iron  or  steel-making  processes  could  eliminate 
these  impurities  without  undue  cost.  The  success  of  this  furnace  is 
due  (1)  to  the  higher  temperature  which  can  be  maintained  and 
regulated  as  compared  with  the  open-hearth  furnace,  and  (2)  to  the 
control  of  the  chemical  reactions  exclusively  through  the  action  of 
the  slag  which  can  be  made  of  the  right  chemical  composition  for 
the  reactions  desired,  and  which  forms  over  the  metal  a  covering 
protecting  it  from  the  oxidizing  or  reducing  action  of  atmospheric 
oxygen. 

In  the  high  temperature  of  the  electric  furnace,  the  chemical 
affinities  of  sulphur  and  phosphorus  for  iron  can  be  overcome  by 
certain  elements  placed  in  the  slag,  and  by  this  means  these  im- 
purities are  reduced  to  within  safe  limits. 

These  furnaces  will  melt  and  refine  the  poorest  grade  of  steel  and 
iron  scrap,  but  it  is  more  economical  to  refine  the  steel  prelimi- 
narily in  the  Bessemer  converter  or  the  open-hearth  furnace  and 
transfer  it  to  the  electric  furnace  for  further  purification. 


CHAPTEE  Y. 

MECHANICAL  TREATMENT  OF  METALS.  HEAT  TREATMENT 

OF  METALS. 

142.  Forms  of  Newly  Produced  Metals. — The  common  metals  are 
taken  in  a  molten  state  from  the  furnaces  which  produce  them  and 
are  cast  into  the  forms  outlined  in  this  and  the  following  paragraph. 
It  must  be  mentioned  that  most  of  the  pig  iron  produced  by  the 
smelting  furnace  is  not  cast  into  form  as  pig  iron,  but  is  converted 
into  steel  without  leaving  the  molten  state,  and  is  cast  as  steel  into 
ingots,  billets  and  steel  castings. 

The  courses  followed  by  metals  immediately  after  they  are  tapped 
from  smelting  furnaces  are  given  in  the  appended  table : 

Metal.  How  disposed  of  when  tapped  from  the  producing  furnace. 

Iron. ...  1.  Conveyed  in  the  molten  state  as  hot  metal  or  direct  metal 
to  the  mixer  or  retaining  reservoir  which  supplies  the 
Bessemer  converter  and  the  open-hearth  steel  furnace; 
or  conveyed  directly  to  these  without  going  to  the 
mixer.  Or,  when  tapped  from  the  smelter  is: 
2.  Cast  into  pigs: 

(a)  To  be  used  in  the  foundry  for  making  castings; 

(b)  To  be  converted  into  wrought  iron  in  the  puddling 
furnace; 

(c)  To  be  remelted  for  steel  making  as  in  item  1. 
Copper . .  3.  Cast  into : 

(a)  Pigs  or   ingots    (about  50  Ibs.)    to  be  remelted   for 
brass  and  other  alloys; 

(b)  Billets  for  making  seamless  copper  tubes  and  pipes; 

(c)  Cakes  for  rolling  into  sheet  copper; 

(d)  Bars  to  be  drawn  into  rods  and  wire. 
Zinc 4.  Cast  into  slabs  for  subsequent  uses. 

Lead 5.  Cast  into : 

(a)  Pigs  for  remelting; 

(b)  Cakes  or  slabs  for  rolling  into  sheets; 

(c)  Bars  for  pressing  through  dies  into  wire  and  lead 
pipe. 

Tin 6.  Cast  into  blocks  for  remelting. 

When  steel  is  produced  it  is  cast  into : 

(1)  Ingots  or  billets  for  rolling  into  various  forms  of  metal 
stock,  or  for  making  very  large  forgings. 

(2)  Steel  castings  of  definite  form  for  specific  uses. 


124  MECHANICAL  PROCESSES 

The  uses  of  the  words  "  ingot "  and  "  billet "  are  somewhat  con- 
fused. In  steel  making,  ingots  are  large  masses  of  steel  usually 
about  20  x  20  inches  in  section  and  5  or  6  feet  long,  but  they  may  be 
smaller  and  even  much  larger  and  of  various  shapes  of  cross  section 
for  particular  reasons.  Small  ingots,  about  6x6  inches  in  section 
and  smaller,  are  called  billets.  Billets  may  be  formed  either 
directly  by  casting  steel  into  billet  moulds,  or  by  rolling  red-hot 
ingots  down  to  billet  sizes.  Billets  are  usually  made  in  specified 
sizes  as  ordered  by  mills  which  manufacture  them  into  a  particular 
class  of  articles,  as  tubes,  rods  for  wire  drawing,  tool  steel,  spring 
material,  etc. 

143.  Primary  Outline  of  the  Shaping  of  Metals. — It  will  be  seen 
from  the  preceding  paragraph  that  all  objects  made  of  iron  and  steel 
may  be  divided  into  two  general  classes  in  regard  to  the  methods 
of  shaping  them.  These  are : 

(1)  Objects  poured  from  molten  cast  iron  or  molten  steel,  and 
known  as  castings. 

(2)  Objects  shaped  by  mechanical  pressure  from  hot-steel  ingots 
and  billets,  or  from  wrought-iron  "  piles  "  bundled  and  heated  for 
welding  together. 

Objects  of  the  first-named  class  are  cast  usually  in  sand  moulds 
made  in  more  or  less  complicated  shapes  to  produce  a  piece  of  metal 
for  a  particular  purpose,  as  a  steam-engine  cylinder  in  cast  iron  or 
stern  and  stem  posts  of  a  ship  in  cast  steel.  Objects  of  this  class 
are  not  hammered,  rolled  or  otherwise  changed  in  shape  for  final 
use  except  the  finishing  of  them  by  more  or  less  superficial  cleaning, 
chipping,  filing  and  machining. 

As  cast  iron  and  steel  castings  are  made  in  the  iron  and  steel 
foundries  respectively,  which  are  subjects  of  another  chapter,  it 
is  not  intended  to  give  them  more  than  general  mention  here.  It 
may  be  stated,  however,  that  small  steel  castings  are  frequently 
made  in  steel  works  of  steel  directly  from  the  converter,  open-hearth 
or  crucible  furnaces;  and  that  very  large  steel  castings  are  neces- 
sarily made  at  steel  works,  where  molten  steel  is  produced  in  large 
quantities,  rather  than  in  the  steel  foundry,  which  is  usually 
equipped  for  producing  steel  only  in  quantities  of  a  few  tons  at  a 
time.  Large  steel  castings  include  such  objects  as  rotor  drums  for 
steam  turbines,  rudder  frames,  stems  and  stem-posts  for  ships, 


MECHANICAL  AND  HEAT  TREATMENT  OP  METALS         125 

hydraulic  cylinders,  gun  carriages.,  etc.,  which  require  a  strength 
and  elasticity  not  possessed  by  cast  iron.  These  castings  are  made 
from  low-carbon  Bessemer  or  open-hearth  steel. 

The  object  of  this  chapter  is  mainly  to  outline  the  mechanical 
operations  of  the  rolling  mill  and  of  the  large  forging  press,  both  of 
which  handle  ingots  of  steel  in  their  primary  forms.  The  rolling 
mills  converts  ingots  and  billets  into  such  well-known  forms  of 
metal  as  rods,  bars,  plates,  railroad  rails,  and  structural  shapes 
used  in  bridge,  ship  and  architectural  construction.  In  these  forms 
metals  are  supplied  as  stock  to  be  re-manufactured  into  articles  for 
mechanical,  agricultural,  domestic  and  many  other  uses. 

Copper,  brass,  the  bronzes  and  other  metals  are  shaped  into  bars 
and  sheets  by  rolling,  and  these  metals,  including  the  ductile  grades 
of  brass  and  bronze,  are  also  shaped  from  their  primary  forms  by 
the  process  of  extruding,  by  which  a  solid  mass  of  metal  is  forced 
hot  or  cold  through  a  die  of  definite  shape  placed  at  the  end  of  a 
steel  cylinder  which  contains  the  metal. 

144.  Reducing  an  Ingot  to  Marketable  Forms. — An  ingot 
stripped  from  its  mould  should  go  while  hot  to  the  soaking  pit,  a 
large  furnace  in  which  it  is  placed  to  be  brought  to  a  red  or  yellow 
heat  preparatory  to  rolling.  From  the  soaking  pit  it  is  transported 
to  the  rolls,  known  specifically  as  the  rolling  mill,  where  it  is  passed 
several  times  back  and  forth  between  heavy  rolls,  the  pressure  of 
which  reduces  its  cross-section  size  and  at  the  same  time  greatly 
increases  its  length. 

This  reduction  is  known  as  breaking  down.  Ingots  rolled  square 
or  nearly  so  in  cross  section  and  left  larger  than  billets  are  called 
blooms.  These  are  used  for  making  large  forgings,  such  as  piston 
rods,  crank  shafts,  connecting  rods,  etc.,  in  engine-building  works. 
Ingots  rolled  flat  and  wide  are  called  slabs.  An  ingot  rolled  into 
blooms,  billets  or  slabs  is  cut  into  suitable  lengths  for  reheating 
and  further  working.  Mills  are  now  constructed  which  handle  an 
ingot  quickly  enough  to  roll  it  into  finished  railroad  rails,  structural 
shapes,  plates,  billets,  etc.,  without  reheating;  but  rods,  bars,  and 
similar  shapes  of  small  cross  section  cannot  be  rolled  directly  from 
a  large  ingot  because  the  metal  gets  too  cold  before  it  can  be  rolled 
so  small,  and  the  amount  of  material  in  an  ingot  would  stretch  out 
too  long  for  practical  handling  in  one  piece  of  small  section. 
9 


126 


MECHANICAL  PKOCESSES 


Steel  blooms  which  come  from  the  rolling  mill  must  not  be  con- 
fused with  wrought-iron  blooms  or  puddle  balls. 

145.  Reheating  of  Ingots.  The  Soaking  Pit.— Although  the 
stripped  ingot  may  be  at  a  glowing  red  heat  as  it  comes  from  the 
mould,,  it  cannot  be  rolled  because  the  interior  is  yet  liquid  and  the 
solid  exterior  would  merely  disrupt  and  allow  the  liquid  interior 
to  squirt  out  under  the  pressure  of  the  rolls.  The  heat  throughout 
the  mass  of  the  ingot  must  be  nearly  equalized  in  order  that  each 
part  may  be  affected  about  alike  under  the  rolls,  although  an  ingot 


FIG.  38. — Soaking  Pit  for  Steel  Ingots. 


rolls  best  when  hotter  at  the  center  than  on  the  surfaces.  To 
equalize  external  and  internal  heat,  i.  e.,  to  stop  the  loss  of  heat 
from  the  exterior  surface  and  allow  it  to  become  heated  from  the 
inside  while,  at  the  same  time,  the  inside  metal  is  solidifying,  the 
ingot  is  placed  in  the  soaking  pit.  The  original  soaking  pit  was 
merely  a  hole  in  dry  ground  lined  with  fire  brick  and  provided  with 
a  thick  fire-brick  cover.  The  ingot  radiated  its  heat  to  the  walls 
of  this  pit  and  the  non-conducting  walls  retained  the  heat  until  the 
ingot  was  of  nearly  equal  temperature  throughout. 

It  frequently  happened  that  ingots  became  too  cold  before  they 


MECHANICAL  AND  HEAT  TREATMENT  OF  METALS 


127 


reached  the  pit,  due  to  unavoidable  delays,  to  be  hot  enough  for 
rolling  after  they  were  "  soaked."  This  condition  necessitated  some 
way  of  supplying  external  heat  to  the  pits.  The  necessity  of  heat- 
ing soaking-pits  has  gradually  developed  the  soaking-pit  shown  in 
Fig.  38.  This,  pit  is  heated  by  the  regenerative  system  described 
with  the  open-hearth  furnace. 

As  soon  as  ingots  are  stripped,  they  are  hauled  to  the  pits,  weighed, 
lifted  by  a  specially  fitted  crane  and  lowered  into  the  pits.     From 


FIG.  39. — View  over  Tops  of  Soaking  Pits. 

6  to  8  ingots  are  placed  in  one  pit,  and  they  are  kept  in  there,  with 
the  pit  covered,  for  an  hour  or  more,  until  they  are  at  or  above  a 
bright  red  heat.  No  gas  need  be  turned  on  if  the  ingot  is  stripped 
very  hot,  and  mere  "  soaking  "  is  all  that  is  needed. 

Fig.  39  shows  a  number  of  soaking  pits.  The  crane  is  in  the  act 
of  lowering  an  ingot  into  an  open  pit.  The  pit  covers  are  slid 
horizontally  by  means  of  hydraulic  cylinders,  marked  C,  in  the 
figure. 


128  MECHANICAL  PROCESSES 

146.  Rolling  an  Ingot. — When  an  ingot  has  reached  the  tem- 
perature for  rolling,  it  is  lifted  from  the  pit  and  carried  by  the 
crane  to  the  ingot  buggy,  where  it  rests  until  a  lever  is  released  to 
dump  it  on  the  roller  table.  The  greater  the  reduction  in  size 
to  be  made  in  the  ingot,  the  hotter  it  needs  to  be,  because  of  the 
longer  time  required  for  rolling.  It  is  best,  when  possible,  to  roll 
the  ingot  to  the  finished  shape  in  a  single  heat,  as  a  second  heating 
adds  to  the  cost  of  the  finished  materials.  An  ingot,  for  example, 
may  be  rolled  into  a  length  of  five  railroad  rails  of  33  feet  each, 
making  1G5  feet  in  one  piece,  and  this  length  could  not  be  reheated 
without  cutting  it  into  pieces  and  much  handling. 

Fig.  40  shows  the  first  stages  in  the  process  of  rolling  a  large 
ingot.  The  mill  in  this  view  is  known  as  a  reversible  blooming  mill. 
This  mill  has  too  heavy  rolls,  the  upper  of  which  is  shown  at  R. 
These  rolls  revolve  in  opposite  directions  and  are  driven  by  a  large 
reversible  engine  or  by  a  motor.  The  function  of  a  blooming  mill 
is  usually  merely  to  reduce  the  cross  section  of  the  ingot  to  a  con- 
venient size  for  finishing  in  smaller  rolls  to  the  exact  cross  section 
desired.  The  ingot  A  rests  on  the  ingot  buggy  R,  awaiting  the 
breaking  down  of  the  ingot  0. 

The  roller  table  consists  of  a  succession  of  horizontal  rollers  TT 
driven  in  unison  by  the  cogged  bevel  wheels  DD  from  a  single  shaft 
running  the  length  of  the  table.  This  table  extends  out  from  both 
sides  of  the  mill,  and  conveys  the  ingot  back  and  forth  into  contact 
with  the  mill  rolls,  which  engage  it  and  send  it  through,  reducing 
its  vertical  dimension  a  given  amount  at  each  pass.  When  the  ingot 
has  passed  through  the  rolls,  it  is  turned  on  its  side  by  a  device 
called  the  manipulator.  The  motion  of  the  table  rollers  and  of  the 
mill  rolls  is  then  reversed,  and  the  ingot  passes  back  between  the 
rolls.  After  each  pass,  the  upper  roll,  R,  is  let  down  a  given  amount 
by  heavy  screws  which  control  its  ends  in  the  mill  housings,  and 
which  are  operated  by  the  mechanism  seen  on  top  of  the  mill,  under 
control  of  the  man  in  charge.  The  roller  table  is  driven  by  a  re- 
versible motor  G. 

After  a  few  passes  through  the  rolls,  the  ingot — or  bloom,  as  it 
may  now  be  called — is  conveyed  along  the  roller  table  to  a  heavy 
hydraulic-shearing  machine  which  cuts  off  the  discard  from  the 
bloom.  The  hvdraulic  shears  are  so  mounted  that  the  roller  table 


MECHANICAL  AXD  HEAT  TREATMENT  OF  METALS 


129 


conveys  material  to  and  from  them  in  the  same  way  that  it  is  con- 
veyed to  the  rolls,  and  these  shears  are  powerful  enough  to  do  their 
work  instantly,  without  loss  of  time. 

After  the  crop  ends  are  sheared  off,  the  bloom,,  still  red  hot,  is 
conveyed  back  to  the  mill.  Its  passage  back  and  forth  between  the 
rolls  is  repeated,  and  it  is  shifted  by  the  manipulator  from  side  to 
side  of  the  roller  table  to  direct  it  into  the  different  sections  or 


FIG.  40. — Starting  an  Ingot  through  the  Blooming  Rolls. 

passes  along  the  rolls  until  it  is  reduced  to  the  size  desired.  It  is 
then  either  cut  into  bloom  length  of  6  feet,  more  or  less,  by  the 
hydraulic  shears,  or  is  conveyed  by  the  roller  table  to  another  mill 
which  rolls  it  in  one  length  into  railroad  rails  or  other  shapes  of 
about  the  same  cross-sectional  area.  -  However,  a  blooming  mill 
may  be  fitted  with  rolls  not  only  to  do  the  work  of  breaking  ingots 
down  into  blooms,  but  to  do  certain  classes  of  finishing,  as  in  rolling 
large  billets  or  large  structural  shapes. 

Throughout  the  rolling,  the  material  is  at  a  red  heat. 


130 


MECHANICAL  PROCESSES 


147.  Mill  Scale. — In  heating  an  ingot  in  the  pit,  particularly  in 
an  oxidizing  flame,  and  in  exposing  the  red-hot  ingot  to  contact 
with  the  atmosphere,  a  film  of  iron  oxide  forms  over  its  surface. 
This  oxide  is  very  brittle,  and  as  soon  as  the  ingot  goes  through  the 
rolls,  it  drops  off  and  falls  through  under  the  mill.    This  is  known 
as  mill  scale  or  roll  scale,  and  is  valuable  for  use  in  wrought  iron 
and  steel  furnaces,  as  has  been  mentioned. 

148.  Structural  Steel  Shapes. — The  use  of  mild  steel  for  struc- 
tural purposes,  i.  e.,  bridge  building,  ship  building,  architectural 
structures,   railroad   and  other  rails,   etc.,   has   developed   certain 
standard  shapes  especially  for  these  needs.     The  object  sought  in 
any  structure  built  for  strength  is  to  dispose   of  the  structural 
material  in  such  a  way  as  to  get  maximum  strength  for  minimum 


I-Beam.       Channel  Bar.        Angle  Bar.  T-Bar. 

FIG.  41. — Structural  Shapes. 


Z-Bar. 


weight  of  material.  This  does  not  mean  that  in  a  structure  the  least 
possible  amount  of  material  must  be  used,  but  it  means  that  the 
required  safe  strength  having  been  determined,  the  material  must 
be  so  disposed  that  a  minimum  weight  of  material  will  suffice  to 
give  this  strength. 

To  carry  out  this  principle,  various  shapes  in  mild  steel  have  been 
standardized,  but  these  shapes  are  not  necessarily  ideal,  and  are 
subject  "to  improvement  under  experimentation.  These  shapes  are 
shown  in  cross  section  in  Fig.  41. 

The  cross-section  form  of  each  size  of  these  shapes  is  standard- 
ized in  area,  thickness,  length,  slope  and  curvature  of  each  part,  and 
each  running  foot  of  length  must  weigh  a  given  amount.  Standard 
shapes  of  similar  section  are  made  of  different  weights  per  running 
foot.  Special  shapes  are  often  rolled  for  particular  uses  or  for  a 


MECHANICAL  AND  HEAT  TREATMENT  OF  METALS        131 

particular  class  of  uses,  and  are  practically  standards  too,  inasmuch 
as  they  are  extensively  used. 

Other  shapes,  for  special  uses  are  shown  in  Fig.  42. 


Bulb  Beam.  Railroad  *  Trolley  Rail.  Tie  Rod  or  Eye  Bar 

For  Decks.  Rail.  For  Bridge  and  Truss  Work. 

FIG.  42. — Special  Shapes. 

Large  steel  mills  issue  an  elaborate  hand-book  giving  much  valu- 
able information  of  sizes,  dimensions,  weight,  strength  and  other 
particulars  of  steel  shapes. 

149.  Types  of  Boiling  Mills. — The  number  of  rolled  products 
now  common  in  the  iron  and  steel  trade,  consisting  of  blooms, 
billets,  structural  shapes,  plates,  rails,  bars,  rods,  etc.,  necessitates 
rolling  mills  of  a  variety  of  types  and  sizes  for  their  production. 

The  largest  mills,  known  as  blooming,  cogging  and  slabbing  mills, 
roll  ingots  into  blooms,  slabs,  or  large  billets.  Some  of  these  mills, 
as  Fig.  44,  have  roll  passes  for  rolling  the  larger  structural  shapes 
immediately  after  other  passes  of  the  rolls  have  broken  the  ingot 
down  into  a  bloom  of  the  required  size.  This  saves  much  expense 
in  reheating.  Figs.  40,  43  and  44  are  examples  of  the  largest  mills. 

Mills  next  in  size  are  in  greater  variety  because  of  the  greater 
diversity  of  products  rolled  by  them.  They  receive  blooms,  slabs, 
and  billets  from  the  heavier  mills,  and  roll  them  into  a  variety  of 
forms  such  as  small  billets,  structural  shapes,  railroad  rails,  sheet 
bars  and  plates. 

The  small  type  of  mills,  known  as  merchant  and  sheet  mills,  re- 
ceive sheet  bars  and  small  billets  from  the  second  group  of  mills. 
Merchant  mills  roll  billets  into  small  rods  and  bars  of  a  great  variety 
of  sizes  and  cross-sections,  known  as  merchant  bar  and  familiarly 
seen  as  stock  in  the  blacksmith  shop.  Sheet  mills  roll  sheet  bars 
into  thin  sheets  commonly  seen  as  sheet  iron. 

*  The  thumb  projection  on  this  rail  projects  horizontally  when  rolled. 
The  last  pass  through  the  rolls  bends  it  up  as  shown. 


132  MECHANICAL  PROCESSES 

Besides  the  foregoing  classification  of  mills  according  to  size  and 
work  they  do,  they  are  also  classified  according  to  design  as  follows : 

(1)  The  reversible  mill  is  one  in  which  the  two  rolls  are  reversible 
and  the  material  rolled  is  fed  between  them  alternately  from  opposite 
sides  of  the  mill.    Figs.  40,  43,  and  44  are  examples  of  this  class. 

(2)  The  three-high  mill  is  one  with  three  rolls,  which  are  not 
reversed.    Fig.  45  is  an  example  of  this  class. 

(3)  The  universal  mill  is  one  which  is  provided  with  a  pair  of 
vertical  rolls  in  addition  to  a  pair  of  horizontal  rolls.     These  four 
rolls  press  on  all  sides  of  a  square  piece  of  material  as  it  passes 
through  the  mill.    Figs.  40  and  44  are  examples. 

(4)  The  pull-over  mill  is  a  small  two-roll  mill  which  is  not  re- 
versible.   This  mill  is  used  for  rolling  thin  sheet  metals.    When  a 
slab  passes  between  the  rolls,  it  is  pulled  back  over  the  top  roll  to 
be  passed  through  again.    A  type  of  this  mill  is  shown  in  Fig,  55. 

(5)  The  continuous  mill  is  a  succession  of  small  two-roll  mills 
placed  near  together  in  line.    They  are  used  to  roll  merchant  bar. 
In  rolling  small  bars  the  metal  loses  its  heat  so  rapidly  that  it  is 
necessary  to  roll  it  quickly.    The  continuous  mill  accomplishes  this 
by  passing  the  material  from  one  set  of  rolls  to  the  next,  and  in  this 
way  a  bar  may  be  in  the  process  of  rolling  between  as  many  as  ten 
pairs  of  rolls  at  once. 

(6)  The  looping  mill  is  another  arrangement  of  several  small  two- 
roll  mills  to  operate  on  small  material  quickly.     These  mills  are 
placed  edge  to  edge  along  a  line  and  a  red-hot  rod  a  hundred  or 
more  feet  long  passes  from  the  first  mill  in  a  U-shaped  loop  through 
the  next,  and  so  on  through  each  successive  mill  in  a  snake-like  curve 
until  it  is  coiled  up  after  passing  through  the  last  mill.     This, 
material   is   used  mostly   for   drawing   into  wire,   which   will   be 
described  later.    As  in  the  continuous  mill,  the  material  is  passing 
through  several  pairs  of  rolls  at  the  same  time. 

150.  The  Cogging  Mill. — Fig.  43  shows  a  cogging  mill,  so  named 
because  its  rolls  are  roughed  or  cogged  to  grip  the  end  of  the 
ingot  firmly  and  force  it  into  the  rolls.  The  blooming  mill  in  Fig.  40 
does  the  same  kind  of  work. 


MECHANICAL  AND  HEAT  TREATMENT  OF  METALS         133 


134 


MECHANICAL  PROCESSES 


151.  The  Structural  Mill. — Fig.  44  shows  a  universal,  reversible, 
structural  mill.  This  mill  has  two  horizontal  rolls  CC,  and  two 
vertical  rolls  DD.  The  mill  shown  in  this  view  is  for  rolling  large 
I-beams,  and  the  vertical  rolls  make  the  top  and  bottom  flange  sur- 
faces parallel.  The  vertical  rolls  are  run  by  beveled-gear  wheels 


FIG.  44. — Universal,  Reversible,  Structural  Mill. 

under  the  casing  Kf  connected  to  the  engine  by  the  shaft  L.  They 
may  be  readily  adjusted  so  that  the  distance  between  them  is  in- 
creased or  decreased.  The  universal  type  of  mill  does  its  work 
more  rapidly  than  is  the  case  with  other  types  of  large  mills.  It 
is  also  much  used  in  rolling  plates  to  avoid  the  necessity  of  trim- 
ming the  plate  edges  after  rolling. 


MECHANICAL  AND  HEAT  TREATMENT  OF  METALS 


135 


152.  The  Billet  Mill.— Fig.  45  shows  a  three-high  billet  mill. 
Each  of  the  rolls  of  this  mill  runs  continuously  in  one  direction  as 
shown  by  the  arrows.  To  allow  a  bloom  (or  a  small  ingot)  to  be  run 
between  the  upper  and  middle  rolls,  this  form  of  mill  is  equipped 
with  lifting  tables.  A  section  of  the  roller  table  about  20  or  30 
feet  long  which  lies  next  to  the  mill  on  each  side  is  so  hinged  that 


FIG.  45.— Three-High  Billet  Mill. 

the  ends  adjacent  to  the  mill  can  be  lifted  to  the  level  B  in  the  figure. 
After  the  bloom  A  passes  through  the  mill  with  the  table  in  the 
position  now  shown,  the  table  ends  on  both  sides  of  the  mill  are 
lifted  by  hydraulic  mechanism.  The  table  rollers,  are  then  re- 
versed and  the  bloom  passes  back  to  this  side.  Both  tables  are 
then  lowered  to  the  position  shown  in  the  figure  and  the  bloom 
is  again  passed  between  the  middle  and  the  lower  rolls. 

The  rolls  of  this  mill  remain  the  same  distance  apart,  and  the 
bloom  is  reduced  by  being  sent  through  the  different  passes  between 


136 


MECHANICAL  PROCESSES 


the  rolls,  which  are  successively  smaller  along  the  rolls.  The  several 
fingers  or  prongs  M  are  for  the  purpose  of  turning  the  bloom  over 
and  directing  it  to  any  pass  through  the  rolls  as  may  be  desired. 
These  fingers  belong  to  the  manipulator,  various  types  of  which  are 
fitted  to  mills,  and  are  so  controlled  by  hydraulic  mechanism  that 
they  can  be  lowered,  raised  and  moved  from  side  to  side  between  the 
rollers  at  will. 

153.  The  Rail  Mill. — Fig.  46  shows  the  several  mills  for  shaping 
railroad  or  street-car  rails.    These  are  three-high  mills. 


FIG.  46.— Rail  Mill. 

The  blooming  mill  first  breaks  the  ingot  down  to  about  8x8 
inches,  the  hydraulic  shears  cuts  off  the  discard  at  the  ends,  and  the 
ramainder  of  the  bloom  is  then  rolled  by  the  mills  shown  in  the 
view. 

Quick  handling  and  several  mills  are  necessary  to  get  the  rail 
shaped  before  it  loses  its  redness,  as  it  is  shaped  completely  without 
reheating.  The  bloom  passes  back  and  forth  through  one  set  of  rolls 


MECHANICAL  AND  HEAT  TREATMENT  OF  METALS         137 

five  times,  is  carried  along  the  roller  table  to  another  set,  which  it 
passes  through  five  times  and  then  it  passes  once  through  the  finish- 
ing rolls  which  merely  smooth  its  surface. 

These  rolls  are  held  the  same  distance  apart  throughout  the  entire 
operation,  and  the  passes  in  them  give  the  desired  shape  to  the  rail. 
When  the  ingot  is  rolled  out  into  a  rail  it  is  something  over  165  feet 
long — 5  rails  of  33  feet  each.  This  length  is  sawed  hot  by  steel 
circular  saws,  shown  at  S  in  Fig.  46,  so  that  when  each  rail  is  cold 
it  measures  33  feet  in  length. 

154.  The  Sheet-Bar  Mill. — Thin  sheets  of  iron  or  steel  are  rolled 
hot   from  bars   about  8   inches  wide  known   as  sheet-bars.     The 
sheet  bars  for  this  industry  are  rolled  in  the  sheet-bar  mill,  not 
unlike  the  billet  mill  in  Fig.  45,  and  the  method  of  rolling  them 
from  the  ingot  or  from  the  wrought-iron  "  pile  "  is  similar  to  that 
mentioned  for  rolling  rails.     The  ingot  is  rolled  out  into  a  long 
strip  8  inches  wide  and  varying  from  %  to  1%  inches  thick.    This 
strip  is  cut  into  lengths  of  30  feet  for  convenience  in  handling,  and 
is  shipped  to  the  sheet  mill,  the  work  of  which  is  described  in  the 
next  chapter. 

The  sJcelp  mill  is  a  special  sheet-bar  mill  for  rolling  steel  or 
wrought  iron  bars  or  "  skelp  "  for  the  manufacture  of  iron  pipe. 

Plates  of  steel  of  i/4-inch  or  less  in  thickness  are  designated  as 
sheets. 

155.  Plate  Mills. — Slabs  from  the  blooming  or  slabbing  mills  are 
reheated  and  rolled  by  the  plate  mill  into  plates  for  many  uses,  in- 
cluding boiler  plates,  ship  plates,  tank  plates,  etc. 

Plate  rolling  was  described  under  the  making  of  wrought  iron. 

The  largest  plates  now  rolled  are  about  145  inches  wide.  The 
length  depends  upon  the  size  of  the  ingot  less  the  discarded  ends. 

In  rolling  plates,  care  must  be  taken  to  keep  the  upper  surface 
of  the  plate  free  of  mill  scale,  which  would  make  a  defective  surface 
if  rolled  into  the  plate. 

156.  Names  of  Rolling-Mill  Parts. — The  more  commonly  desig- 
nated rolling-mill  parts  include  rolls,  housings,  roller  table,  manip- 
ulator, guides,  guards,  passes,  and  collars.     Several  of  these  parts 
have  been  mentioned. 


138 


MECHANICAL  PROCESSES 


Fig.  47  shows  the  outline  of  a  pair  of  rolls  with  examples  of 
typical  passes  between  the  rolls.  A  and  C  are  open  passes,  i.  e.,  a 
fin  of  metal  may  be  squeezed  out  from  the  sides  of  the  billet  if  it 


FIG  47. — Forms  of  Passes  in  Rolls. 

is  pressed  hard  enough.  To  avoid  the  forming  of  a  side  fin,  the 
closed  pass  B  is  used.  F,  F,  are  collars  on  the  rolls.  C  is  called 
a  diamond  pass,  and  D  is  a  bearing  to  support  the  upper  roll  be- 
cause of  its  great  reduction  of  diameter  at  the  middle. 


FIG.  48. — Example  of  Rolling  an  Angle  Bar. 

Fig.  48  shows  six  passes  necessary  for  rolling  a  billet  into  angle 
bar  of  unequal  legs.  Successive  changes  in  cross-section  from  the 
billet  to  the  finished  shape  must  be  gradual,  as  here  shown.  The  hot 


MECHANICAL  AND  HEAT  TREATMENT  OF  METALS         139 

material  could  not  stand  a  radical  change  between  successive  shapes, 
as  it  would  tear  or  distort.  To  avoid  stretching  one  leg  of  the  bar 
more  than  the  other  in  rolling,  the  passes  must  be  so  made  that  the 
two  ends  of  the  legs  will  lie  in  a  line  parallel  to  the  axis  of  the  roll. 
Both  rolls  run  at  the  same  number  of  revolutions  per  minute,  but 
the  upper  roll  is  slightly  larger  in  diameter  than  the  lower  roll  so 
that  the  rolled  material  will  peel  from  the  upper  roll.  To  make  the 
material  peel  from  the  lower  roll  when  the  first  end  passes  through, 
a  guard  is  fitted,  as  in  Fig.  49.  To  prevent  material  from  being 
engaged  by  the  roll  collars,  and  to  direct  it  into  the  right  passes, 
guides  are  fitted  as  shown  in  Fig.  49.  Fig.  45  shows  guides  leading 


FIG.  49. 

to  the  lower  roll,  and  guards  may  be  seen  along  the  piece  marked 
B  in  that  figure. 

Finishing  rolls,  which  do  not  exert  much  pressure,  and  plain 
rolls  for  plates  and  sheets,  are  made  of  cast  iron  with  the  roll  sur- 
face chilled  to  harden  it.  Blooming  and  roughing  rolls  are  made 
of  cast  steel  to  withstand  the  enormous  shocks  of  heavy  work. 
Structural  rolls  are  made  of  cast  steel. 

Roll  surfaces  are  first  turned  to  shape  in  large  lathes  and  are 
then  ground  by  special  appliances  to  a  true  surface. 

157.  Reheating  of  Blooms,  Slabs  and  Billets.— Reheating  fur- 
naces are  of  many  forms  according  to  the  fuel  used,  the  size  and 
shape  of  the  material  to  be  reheated,  and  the  rapidity  demanded 
in  handling  the  heated  material.  The  largest  types  of  reheating 
furnaces  are  those  used  for  heating  armor  and  other  large  ingots 


140 


MECHANICAL  PROCESSES 


to  be  shaped  under  the  hydraulic  forging  press.  These  furnaces 
are  heated  usually  by  the  regenerative  system.  The  smallest  types 
are  possibly  the  small  portable  oil-burning  furnaces  for  heating 
rivets,  and  used  also  for  heating  small  material  to  be  forged.  The 
fuels  used  are  long-flame  coal,  crude  oil,  or  gas,  and  usually  a  smoke 
stack  is  necessary  to  take  away  the  products  of  combustion,  but 


FIG.  50. — Furnace  for  Reheating  Billets. 

many  oil  and  gas  furnaces  have  no  smoke  stacks.  The  reverbera- 
tory  type  of  furnace,  with  end  or  side  door  in  the  fuel  space,  and 
end  or  side  doors  in  the  heating  space,  according  to  the  convenience 
of  each  specific  case,  is  much  used  for  reheating. 

Fig.  50  shows  a  small  furnace  for  reheating  billets.  This  is 
-equipped  for  burning  oil  and  has  a  door  at  each  end.  The  flame 
from  the  oil  burner  (at  the  side)  is  directed  into  the  heating  space 
through  a  hole  in  the  furnace  wall. 


MECHANICAL  AND  HEAT  TREATMENT  OF  METALS         141 


10 


142  MECHANICAL  PROCESSES 

A  reheating-furnace  bottom  is  usually  a  flat  magnesite  bottom, 
sloping  slightly  to  one  side.  The  soaking-pit  is  a  reheating  fur- 
nace, but  it  is  adapted  only  to  ingots,  which  can  stand  on  end. 

The  continuous  furnace  is  a  type  much  used.  This  is  equipped 
with  a  gravity  slide  or  suitable  mechanism  for  moving  a  continuous 
line  of  material  through  the  furnace  in  a  given  time,  and  the  heat- 
ing is  accomplished  while  the  material  is  passing  through. 

158.  Reheating  Furnace  for  Large  Blooms. — Fig.  51  shows  the 
front  of  a  regenerative  heating  furnace  for  blooms  and  other  large 
material,  with  the  charging  crane  used  to  handle  heavy  material. 
This  furnace  is  modeled  like  the  open-hearth  steel  furnace.     The 
whole  of  one  side  is  enclosed  by  doors  D,  which  open  into  one  com- 
mon heating  space.     Connection  with  the  regenerative  heating  sys- 
tem at  one  end  of  the  furnace  is  shown  at  R. 

The  crane  has  an  arm  A,  with  electrically  controlled  tongs  or 
fingers  at  the  end,  which  now  holds  a  bloom  ready  to  be  conveyed 
through  the  open  door  into  the  furnace.  This  arm  may  be  swung 
in  a  horizontal  plane,  with  slight  vertical  movement  for  lifting  or 
lowering  blooms.  The  roller  table  T  may  be  used  to  convey  cold 
blooms  within  reach  of  the  crane,  and  to  convey  hot  blooms  to  the 
hydraulic  shears  in  the  background  of  the  view. 

159.  Precautions  in  Reheating  High-Grade  Steel. — To  avoid  the 
formation  of  scale  in  reheating  metals,  i.  e.,  the  waste  of  the  sur- 
face by  oxidation,  the  furnace  flame  should  be  a  reducing  and  not 
an  oxidizing  flame.    Xo  risks  of  oxidation  can  be  taken  with  high- 
carbon  and  alloy  steels  (usually  crucible  steels)   as  any  change  in 
the  carbon  or  alloying  metal  would  reduce  the  quality  of  the  steel. 
To  avoid  oxidation,  each  billet  is  coated  with  fire  clay,  sand  and 
borax,  or  other  harmless,  refractory  mixture,  and  placed  in  the 
furnace.    After  removing  from  the  furnace,  this  mixture  is  broken 
off  before  the  billet  goes  to  the  rolls  or  the  hammer. 

160.  Points  for  the  Inspection  of  Rolled  Material. — Steel  may 
be  good  or  bad  in  quality  due  to  the  substances  it  contains,  and 
steel  which  is  good  when  tapped  from  the  furnace  may  be  made 
bad  by  subsequent  casting,  reheating  and  mechanical  treatment. 
Rolling  improves  the  strength  of  a  metal  and  tends  to  cover  up 
defects. 


MECHANICAL  AND  HEAT  TREATMENT  OF  METALS         143 

Specifications  for  metals,,  particularly  iron  and  steel,,  usually  re- 
quire (1)  surface  inspection,  (2)  physical  testing,  which  is  the 
actual  pulling  and  bending  of  specimens  of  the  metal,  to  determine 
its  strength  and  ductility,  and  (3)  chemical  analysis  to  determine 
its  chemical  constituents.  It  is  intended  to  mention  here  only  the 
requirements  of  surface  inspection,  as  the  defects  so  disclosed  are 
closely  associated  with  casting  and  subsequent  rolling  or  forging  of 
metals. 

Specifications  usually  provide  that  the  surfaces  of  metals  shall 
be  free  from  the  following-named  defects : 

(1)  Slag.  (6)  Sand  or  scale  marks. 

(2)  Foreign  substances.  (7)  Scabs. 

(3)  Brittleness.  (8)  Snakes. 

(4)  Laminations.  (9)  Pits. 

(5)  Hard  spots. 

These  defects  are  usually  caused  by : 

(1)  Slag  and  oxides  which  entered  the  ingot  or  billet  mould 
from  the  ladle. 

(2)  The  chilling  of  ingot  corners  in  cold  moulds,  and  surface 
laminations  and  shot  caused  by  pouring  metal  against  the  sides  of 
the  mould  and  thus  chilling  it. 

(3)  The  sudden  chilling  of  the  surface  of  a  hot  ingot,  billet, 
bloom,  or  slab  when  it  is  taken  from  the  mould  or  reheating  fur- 
nace, causing  small  surface  cracks  called  snakes.     These  cracks, 
when  not  too  numerous  nor  too  deep,  are  chipped  from  the  surface 
before  the  material  is  rolled  or  forged,  as  their  sides  do  not  weld 
together  when  the  metal  is  rolled. 

(4)  Failure  to  discard  enough  of  the  ends  of  an  ingot  or  a  billet. 

(5)  Squeezing  metal  in  rolling  so  that  fins  press  out  between 
the  rolls,  and  subsequently  rolling  these  fins  down  as  laminations 
or  hard  streaks. 

(6)  Not  cleaning  the  mill  scale  from  the  upper  surface  in  roll- 
ing plates,  or  other  wide  shapes,  from  which  scale  will  not  readily 
fall  away  due  to  the  movements  and  jolting  of  the  rolls. 

Further  than  the  defects  named,  rolled  products  should  not  be 
crooked  or  warped,  nor  should  plates  show  undue  variation  of 
thickness  across  their  width  nor  along  their  length. 


144  MECHAXICAL  PROCESSES 

It  is  a  common  practice  to  keep  a  record  of  the  identity  of  every 
ingot  and  billet  cast,  as  in  this  way  many  defects  in  finished  pro- 
ducts may  be  traced  back  to  their  causes. 

161.  Effect  of  Mechanical  Treatment  of  Metals. — The  pressure 
of  the  rolls  and  the  impact  of  the  forging  hammer  on  a  piece  of 
metal  increase  the  strength  of  the  metal  from  2  to  5  times,  accord- 
ing to  the  composition,  the  degree  to  which  the  metal  is  heated,  and 
the  pressure  applied.     The  composition  of  a  metal  determines  its 
ductility  and  the  degree  to  which  its  form  can  be  changed  by  work- 
ing, while  the  heat  and  pressure  to  which  it  is  subjected  determine 
the  depth  to  which  the  rolling  or  hammering  is  effective.   The  roll- 
ing of  a  cold  metal  makes  the  surface  very  hard.   The  strength  of  a 
metal  is  increased  by  rolling  or  hammering  because  (1)  blow  holes 
(including   microscopic   gas   cavities   throughout  the   metal)    are 
pressed  very  small,  and  because  (2)  mechanical  pressure  crowds  the 
metal  crystals  more  closely  together,  breaking  up  planes  of  cleavage 
along  which  tearing  would  naturally  take  place.    The  second  effect 
increases  strength  and  hardness,  but  decreases  ductility  and  the  per 
cent  of  elongation  before  breaking.     Working  a  metal  very  hot 
does  not  cause  marked  changes  in  its  crystalline  structure  because 
the  crystals  are  more  or  less  mobile  according  to  the  heat,  and  are 
helped  by  the  heat  to  assume  their  natural  positions  relative  to  one 
another. 

Two  ingots  from  the  same  heat,  i.  e.,  produced  from  the  same 
heat  in  a  converter  or  furnace,  will  show  different  elastic  and  tensile 
strengths  and  different  degrees  of  elongation  according  to  the  degree 
of  reduction  each  undergoes  in  rolling  or  hammering. 

162.  Cold-Rolled  Steel. — The  colder  a  metal  is  when  rolled  or 
hammered,  the  greater  the  resulting  hardness.     The  depth  of  the 
hardness  depends  upon  the  depth  to  which  the  rolling  or  hammering 
pressure  penetrates. 

There  is  extensive  use  for  steel  rods  and  bars  which  have  hard, 
smooth  surfaces,  both  for  the  hardness  and  for  the  smoothness. 
These  resist  wear  and  take  an  excellent  polish.  They  also  show 
smoothly  when  nickel-plated.  Also,  a  hot-rolled  rod  or  bar  cannot 
be  rolled  to  exact  dimensions,  as  cooling  after  rolling  decreases  its 
cross-section  area  an  uncertain  amount.  To  produce  small  steel 
bars  and  rods  which  are  hard,  smooth,  and  of  exact  dimensions  in 


MECHANICAL  AND  HEAT  TREATMENT  OF  METALS         145 

cross-section,  cold  rolling  is  resorted  to.  The  metal  is  first  rolled  hot 
to  near  the  finished  size,,  pickled  to  remove  the  oxidized  coating 
and  is  then  passed  many  times  between  chilled  rolls.  Kods  up  to 
5  inches  in  diameter  are  rolled  in  this  way,  and  the  resistance  to 
twisting,  due  to  so  hard  a  surface,  makes  this  product  useful  as 
shafting  for  transmitting  power  in  shops. 

163.  Large  Forgings. — Many  massive  steel  products,  as.  armor 
plate,  large  gun  parts,  and  large  shafting  for  marine  engines  or 
turbines,  cannot  be  rolled  because  of  their  shape,  or  because  their 
size  makes  rolling  far  more  expensive  than  forging.    These  products 
are  shaped  from  unusually  large  ingots  which  are  forged  either 
under  impact  of  the  steam  hammer,  or  preferably  pressed  under 
the  hydraulic  forging  press. 

The  blow  of  the  steam  hammer  is  delivered  quickly,  and  its  force 
is  absorbed  at  first  locally  by  the  metal  directly  under  the  impact 
of  the  hammer,  and  as  this  becomes  compacted,  the  force  is  trans- 
mitted deeper  into  the  metal  mass.  The  hydraulic  forging  press  is 
preferable  to  the  hammer  for  large  forgings  because  its  pressure 
makes  itself  felt  entirely  through  the  metal  mass. 

Some  large  forgings  are  made  from  rolled  blooms,  but  these  are 
commonly  made  in  large  manufacturing  plants,  as  shipbuilding 
plants  and  locomotive  works,  by  means  of  steam  hammers. 

164.  The  Hydraulic  Forging  Press. — Fig.  52  shows  a  press  for 
heavy  work.     The  diagram  in  Fig.  53  shows  the  interior  features 
of  the  press. 

This  equipment  consists  of  the  press,  the  hydraulic  intensifier, 
and  the  auxiliary  water  tank. 

A  piece  of  work  W  is  pressed  between  the  dies  DD'.  Different 
shapes  of  dies  may  be  used.  The  press  head  H  is  forced  down  by 
hydraulic  pressure  on  the  ram  P  in  the  cylinder  Nf  and  is  raised 
by  steam  pressure  under  the  two  pistons  in  the  cylinders  CC.  The 
vertical  motion  of  the  press  head  is  guided  by  the  four  colums  G 
which  conect  the  anvil  with  the  entablature  B  and  hold  the  press 
rigidly  against  distortion. 

Water  pressure  of  about  5500  Ibs.  per  square  inch  is  supplied 
through  the  pipe  0  from  the  steam  intensifier  which  consists  essen- 
tially of  a  steam  cylinder  J  and  a  much  smaller  hydraulic  cylinder 
K.  Steam  admitted  under  the  piston  in  J  communicates  the  pres- 


146 


MECHAXICAL  PROCESSES 


sure  to  the  water  in  A"  through  the  rod  L.  Knowing  the  pressure 
per  square  inch  of  steam  in  J ' ,  the  water  pressure  per  square  inch 
in  the  hydraulic  system  is  found  from  the  relation 


FIG.  52. — Hydraulic  Forging  Press. 
Steam  pressure  per  sq.  in.  in  J      Area  of  end  of  plunger  L 


Water  pressure  per  sq.  in.  in  K      Area  of  lower  face  of  piston  in  -7 

A  mechanism  is  fitted  to  shut  off  the  steam  automatically  in  case 
the  water  pressure  in  K  is  suddenly  lost  by  any  accident. 


MECHANICAL  AND  HEAT  TREATMENT  or  METALS        147 


The  entire  working  of  the  press  is  controlled  by  a  single  hand- 
lever  ingeniously  connected  to  control  the  valves  numbered  1,  2,  3 
and  4. 


ft 

<  If 

°*\ 

.. 

I' 

m 

^  / 

PIG.  53. — Diagram  of  Hydraulic  Forging  Press. 

Valve  No.  1  controls  steam  to  the  cylinder  J,  No.  2  controls  ex- 
haust from  the  cylinder  J,  Xo.  3  controls  steam  and  exhaust  from 
the  cylinders  CC,  and  No.  4  controls  water  to  and  from  the  tank  T 
through  the  valve  M. 


148  MECHANICAL  PROCESSES 

The  auxiliary  tank  T  contains  air  and  water  under  a  pressure  of 
60  Ibs.  per  square  inch,  and  is  used  as  a  reservoir  for  supplying 
water  to  or  receiving  it  from  the  main  pipe  0.  The  plunger  L  may 
remain  quiet  and  the  press  head  may  be  lowered  by  allowing  water 
to  flow  through  the  valve  M  from  the  pressure  tank.  Likewise,  the 
press  head  may  be  raised  by  the  cylinders  (7(7,  with  the  valve  M 
opened  to  admit  water  to  the  tank  against  the  tank  pressure.  The 
system  is  so  arranged  that  when  L  moves  upward  the  valve  M  will 
close,  as  great  pressure  must  not  be  communicated  to  the  tank  T. 

165.  Handling  Large  Ingots  for  Forging. — Special  equipment 
must  be  installed  to  transport  large  ingots  between  the  reheating 
furnace  and  the  forging  press  and  to  hold  them  for  the  work  of 
forging.  The  furnace  and  the  press  are  located  conveniently  near 
each  other,  and  a  specially  built  traveling  crane  is  installed  for  this 
work. 

The  upper  end  of  every  ingot  made  for  forging  is  a  ee  crop-end." 
This  end  is  used  to  hold  the  ingot  for  forging  and  is  cut  off  when 
the  forging  is  completed.  This  end  is  cast  smaller  than  the  body  of 
the  ingot  and  is  called  the  "  chuck  stub  "  in  the  forge  shop.  Fig. 
54  shows,  the  equipment  for  holding  ingots.  It  consists  of  a  cliuck 
B,  shown  partly  in  section ;  a  porter  bar  P  for  balancing  and  guid- 
ing the  chuck  and  ingot ;  and  an  endless  chain  C  suspended  from  a 
block  D.  The  whole  equipment  is  suspended  from  and  transported 
by  the  crane. 

The  chuck  stub  is  clamped  by  the  set  screws  in  the  open  end  of 
the  chuck.  The  porter  bar  is  attached  to  the  other  end  of  the  chuck. 
The  swivel  block  D  allows  the  apparatus  to  be  turned  readily  in  a 
horizontal  plane.  The  heavy  spiral  spring  between  the  swivel 
block  and  the  crane  hook  relieves  the  crane  of  any  undue  shock  in 
forging.  It  is  frequently  necessary  to  hang  heavy  iron  weight  to 
the  end  of  the  porter  bar  to  balance  ingot,  chuck,  and  bar  nicely  on 
the  chain.  In  this  way  the  forge  men  can  easily  swing  the  work 
by  hand  pressure  on  the  porter  bar.  The  ingot  is  turned  on  its 
horizontal  axes  by  ratchet  attachment  geared  to  the  groove  G,  or 
it  may  be  turned  by  an  iron  bar  placed  in  one  of  the  holes  beside 
the  groove. 


MECHANICAL  AND  HEAT  TREATMENT  OF  METALS        149 


When  the  ingot  is  carried  to  the  furnace  for  reheating,  which 
may  be  necessary  a  number  of  times  in  the  course  of  making  the 
forging,  the  chuck  stub  sticks  out  of  the  furnace  door,  and  the 
space  below  the  door,  when  it  is  closed  down  on  the  stub,  is  stopped 
temporarily  with  bricks. 

Many  different  chucks  and  porter  bars  are  provided  in  a  large 
forge  shop,  and  some  of  the  porter  bars  axe  60  feet  long  and  nearly 


!  Q 


FIG.  54. — Chuck  and  Porter  Bar. 

a  foot  in  diameter,  which  gives  an  idea  of  the  heavy  forgings 
handled.  Gun  tubes  are  forged  by  the  processes  just  described. 
Some  forging  presses,  as  for  forging  car  wheels,  use  an  intensified 
pressure  of  40,000  Ibs.  or  more  per  square  inch. 

166.  The  Heat  Treatment  of  Metals.— An  essential  part  in  the 
mechanical  shaping  of  a  metal  is  the  heating  required  to  make  it 
easily  workable  without  injury  to  its  strength  and  other  properties. 
Heat  treatment  includes  all  heating  from  the  time  a  metal  is  cast 


150  MECHANICAL  PROCESSES 

into  ingots  or  billets  until  it  goes  out  in  the  form  of  finished  prod- 
ucts. This  is  a  very  extensive  subject  which  is  now  recognized  as 
highly  important  by  manufacturers  of  all  metal  articles,  particu- 
larly so  by  manufacturers  of  articles  in  steel,  because  heating  not 
only  makes  metals  plastic,  but  it  changes  the  crystalline  structure 
of  most  of  them,  affecting  their  strength,  ductility  and  other  use- 
ful properties. 

Carbon  and  iron  are  associated  in  several  different  relations  which 
are,  according  to  investigators,  more  or  less  stable  or  complicated 
chemical  combinations,  all  of  which  may  exist  in  the  same  mass  of 
steel,  and  each  of  which  imposes  certain  properties  on  the  metal 
and  is  affected  in  different  ways  by  heat.  This  condition  makes 
steel  very  complex,  but  a  careful  study  of  all  these  characteristics 
and  of  the  experimental  effects  of  several  kinds  of  treatment  have 
brought  out  much  useful  knowledge  on  the  proper  methods  of  heat- 
ing steel.  Other  metals  are  far  less  complex,  and  the  changes  which 
come  to  them  in  heat  treatment  are  much  simpler.  , 

167.  Changes  in  Steel  Due  to  Heating. — It  is  necessary  to  heat 
steel  not  only  to  shape  it,  but  to  anneal  and  harden  it.  That  heat- 
ing for  any  of  these  purposes  may  be  properly  done,  it  is  necessary 
to  understand  certain  peculiarities,  particularly  of  high-carbon 
steels  (those  containing  .2$  and  over  of  carbon). 

As  steel  rises  in  temperature  it  reaches  a  point,  about  1400°  F. 
(red  heat),  called  the  absorption  point,  at  which  it  absorbs  a  per- 
ceptible amount  of  heat  before  its  temperature  again  increases. 
Likewise,  having  been  raised  above  the  absorption  point  and  allowed 
to  cool  slowly,  it  reaches  a  temperature  about  50°  F.  below  the 
absorption  point  where  it  seems  to  give  out  more  heat  than  is  ac- 
counted for  by  loss  of  temperature.  Its  glow  shows  an  increase  of 
brightness  if  observed  in  a  dark  room.  This  is  the  recalescence  point. 
Both  of  these  points  are  known  as  critical  points. 

Heating  to  the  absorption  point  brings  the  grain  of  steel  to  its 
finest  texture.  The  higher  the  heating  beyond  this  point  and  the 
lower  the  carbon,  the  larger  the  resulting  crystals  upon  cooling. 
This  may  be  seen,  in  many  cases,  by  examining  fractured  specimens 


MECHANICAL  AND  HEAT  TREATMENT  OF  METALS        151 

with  the  unaided  eye.  This  enlargement  of  crystals  reduces 
strength,  hence  the  size  of  crystals  is  a  visible  sign  indicating 
strength.  The  smallest  crystals  may  be  restored  in  high-carbon 
steel  by  heating  it  to  the  absorption  point.  It  may  then  be  cooled 
slowly  or  suddenly  without  change  of  grain. 

Steel  need  never  be  heated  above  its  absorption  point  except  to 
have  it  amply  hot  for  shaping  in  a  single  heat.  If  high-carbon 
steel  is  heated  much  above  the  absorption  point,  its  strength  is 
injured,  its  fracture  looks  dull,  and  it  is  said  to  be  "  burned/'  Such 
a  condition  may  be  impossible  to  remedy.  However,  low-carbon 
steel  escapes  injury  at  high  heats  in  most  instances,  but  becomes 
brittle  if  heated  repeatedly  below  1650°  F.  It  is  restored  to  its 
elasticity  if  heated  above  1650°  F. 

The  crystalline  structure  of  a  piece  of  steel  as  affected  by  heat  is 
determined  by  the  five  conditions  as  follows : 

(1)  Temperature,  (2)  duration  of  heating,  (3)  mass,  (4) 
rapidity  of  cooling,  and  (5)  whether  or  not  steel  cools  without  be- 
ing rolled,  hammered,  or  otherwise  subjected  to  pressure  or  impact. 

The  presence  of  nickel,  tungsten  and  other  metals  used  to  pro- 
duce alloy  steels  have  a  marked  effect  upon  the  critical  points  of 
steel.  These  points  are  lowered,  and  the  presence  of  the  alloying 
metals  seems  to  accomplish  this  by  their  influence  upon  the  carbon 
which  the  steel  contains. 

168.  Annealing-  of  Metals. — When  a  metal  is  heated  to  unequal 
degrees  throughout  its  mass,  or  the  parts  of  the  mass  are  cooled  at 
different  rates,  as  is  common  with  large  forgings  or  large  castings, 
or  when  hammering,  rolling,  or  other  work  is  done  on  cold  metal  to 
change  its  shape,  an  arrangement  of  crystals  is  forced  upon  the 
metal  such  that  some  parts  of  the  mass  are  under  stress.  For  ex- 
ample, a  large  forging  or  casting  may  cool  quickly  on  the  surface 
and,  by  contracting,  pull  the  hotter  parts  of  the  interior  into  a 
shape  which  they  would  not  assume  naturally  as  they  cool.  Ex- 
cessive hammering  or  rolling  makes  cold  metals  brittle.  In  steels, 
internal  stresses  and  brittleness  are  most  marked  when  the  per  cent 
of  carbon  is  greatest. 


152  MECHANICAL  PROCESSES 

Internal  stresses,  which  may  be  dangerous  in  man}''  cases,  and 
brittleness  in  metals  worked  cold,  are  relieved  by  annealing.  This 
consists  of  heating  the  mass  to  a  red  heat  and  allowing  it  to  cool 
very  slowly  in  the  case  of  steel,  or  plunging  into  water  in  the  case 
of  copper  and  some  of  the  copper  alloys.  Annealing  brings  metals 
to  their  softest  and  most  ductile  states. 

Steel  should  be  heated  to  the  absorption  point  for  best  results 
and  finest  grain  in  annealing,  though  this  is  not  always  done 
possibly  because  its  importance  is  not  well  understood.  Steels 
purposely  hardened  would  lose  their  hardness  if  annealed  at  a  high 
heat,  though  they  may  be  partially  annealed  by  moderate  heating 
in  oil  or  molten  lead,  which  will  relieve  the  greatest  stresses. 

Slivers  have  been  known  to  break  and  fly  with  considerable  force 
from  extremely  hard  projectiles  while  they  were  awaiting  annealing, 
due  to  internal  stresses. 

Annealing  is  usually  done  in  furnaces  not  unlike  reheating  fur- 
naces, though  the  degree  of  heat  is  not  so  great  in  annealing  as  in 
reheating  for  working.  Coal  or  wood  fires  can  be  better  regulated 
to  maintain  the  low  temperatures  needed  in  annealing.  To  prevent 
oxidation  in  annealing,  particularly  with  thin  or  delicate  pieces, 
the  material  is  placed  in  a  muffle  furnace  which  transmits  heat 
through  a  brick  partition  to  it,  thus  preventing  contact  with  the 
flame,  or,  better,  the  pieces  are  placed  in  cast-iron  boxes,  the  lids 
of  which  are  luted  with  clay,  and  these  boxes  with  their  contents 
are  placed  in  an  ordinary  furnace. 

Steel  forgings  and  castings  demand  slow  cooling  for  proper  an- 
nealing, and  it  is  a  common  practice  to  heat  them  for  two  or  three 
days  in  a  furnace,  then  seal  up  all  furnace  openings  with  clay  and 
allow  several  days  for  the  furnace  and  contents  to  cool  gradually. 

All  annealing  furnaces  must  be  fitted  with  pyrometers  to  gage 
the  degree  of  heat  in  obtaining  the  best  results. 

169.  The  Hardening  of  Steel. — Steels  containing  above  .25^  of 
carbon  (approximately)  will  become  hardened  if  heated  to  or  above 
the  absorption  point  and  suddenly  cooled,  in  water  or  by  other 
means.  The  degree  of  hardness  depends  upon  (1)  the  amount  of 
combined  carbon,  (2)  the  rapidity  of  cooling,  and  (3)  upon  the 


MECHANICAL  AND  HEAT  TREATMENT  or  METALS        153 

range  of  temperature  through  which  cooling  takes  place  below  the 
absorption  point.  The  rate  of  cooling  of  a  piece  of  metal  is  de- 
pendent upon  its  mass,  as  well  as  upon  its  degree  of  temperature 
above  that  of  the  cooling  medium. 

These  statements  do  not  apply  to  steels  alloyed  with  manganese 
and  tungsten.  They  harden  by  being  heated  nearly  to  melting 
heat  and  being  cooled  fairly  rapidly  in  a  blast  of  air.  In  this  con- 
dition they  do  not  lose  their  hardness  when  raised  to  a  red  heat, 
and  can  be  used  at  a  red  heat  for  cutting. 

170.  Oil   Tempering   of   Steel. — Much   medium-carbon   steel   is 
alloyed  with  nicked,  chromium  or  vanadium  to  provide  material  of 
superior  strength  and  elasticity  for  moving  parts  of  marine  engines, 
automobile   parts   and   other   fittings   where   lightness   and   great 
strength  are  desirable  in  a  steel  of  moderate  cost.     The  strength 
and  reliability  of  these  forgings  are  increased  by  a  process  of  heat- 
ing to  a  red  heat,  quenching  in  oil  (a  residue  of  petroleum  or  a 
fish  oil)  and  then  annealing  slightly.    The  effects  of  this  treatment 
vary  with  different  percentages  of  contained  carbon  and  with  differ- 
ent quenching  temperatures.     These  have  been  studied  and  tabu- 
lated at  some  length  by  investigators.     Gun  forgings,  and  in  some 
processes,  armor  and  projectiles,  are  oil  tempered. 

171.  Kolling  Sheet  Copper.     The  Sheet  Mill. — For  the  manu- 
facture of  sheet  copper,  the  metal  is  cast  either  direct  from  the  re- 
fining furnace,  or  from  remelted  pigs,  into  flat  cakes  3  or  4  inches 
thick.     As  soon  as  these  cakes  have  "  set "  they  are  dumped  into 
cold  water  to  make  them  soft  for  rolling.     They  must  be  not  less 
than  99.75$  pure  for  rolling,  though  all  of  the  impurity  allowed 
must  not  be  wholly  arsenic,  bismuth  or  antimony,  because  the  cakes 
may  crack  slightly  on  the  surface  in  rolling. 

As  soon  as  the  cakes  have  cooled,  their  surfaces  are  examined 
for  spots  of  cinder,  oxide,  scale,  etc.  Large  spots  are  chipped  out, 
or  the  whole  cake  may  be  pickled  in  dilute  sulphuric  acid  and  then 
scrubbed  and  rinsed  to  remove  all  surface  scale.  The  cakes  are 
taken  over  to  the  rolling  mill  and  several  are  heated  at  a  time  to 
redness  in  a  reheating  furnace  in  order  to  keep  the  rolls  supplied. 


154 


MECHANICAL  PROCESSES 


One  cake  at  a  time  is  taken  from  the  furnace  and  passed  re- 
peatedly through  rolls  such  as  are  shown  in  Fig.  55.  This  view 
shows  three  26-inch  pull-over  sheet  mills.  This  type  of  mill 
is  used  for  rolling  thin  sheets  of  commercial  metals,  and  is  called  a 
pull-over  mill  because  a  man  on  the  far  side  of  the  rolls  receives  the 
sheet  as  it  comes  through  and,  by  aid  of  tongs  and  a  guide  bar,  lifts  it 
so  that  the  man  on  the  front  side  can  pull  it  over  the  top  roll  to  pass 
it  again  between  the  rolls. 


FIG.  55. — Sheet  Mills,  Pull-Over  Type. 

If  the  sheet  is  to  be  finished  as  soft  copper,  it  is  rolled  hot  down 
to  the  thickness  required,  is  then  annealed  in  a  furnace  to  make  it 
of  uniform  softness  throughout,  and  is  pickled  to  remove  roll  and 
furnace  scale.  The  sheet  is  then  straightened  by  sending  it  through 
straightening  rolls,  or  it  may  be  straightened  in  a  stretching 
machine  which  grips  the  ends  and  pulls  the  sheet. 

If  the  sheet  is  to  be  finished  as  hard  copper,  suitable  for  making 
pipes,  or  tanks  which  must  stand  pressure,  it  is  rolled  hot  nearly  to 
the  finished  thickness,  pickled,  and  then  rolled  cold  in  the  finishing 
rolls  down  to  gage.  It  is  then  straightened  and  trimmed  to  size. 


MECHANICAL  AND  HEAT  TREATMENT  OF  METALS         155 

To  avoid  the  formation  of  furnace  scale  when  heating  copper  and 
brass  to  be  rolled,  it  is  a  common  practice  to  do  the  heating  and 
annealing  in  muffle  furnaces. 

Cold  rolling  increases  tensile  strength,  but  makes  copper  and 
brass  more  brittle  and  springy,  which  is  a  decrease  in  ductility. 

Sheets  of  copper,  known  as  planished  copper,  which  are  springy 
and  show  highly  polished  surfaces,  are  cold  rolled  after  having 
been  hot  rolled  and  pickled. 

172.  Rolling  of  Sheet  Brass. — Brass  of  the  usual  compositions  is 
rolled  cold  into  sheets  or  other  forms  because  the  metal  will  not 
roll  hot.     However,  if  the  brass  contains  less  than  about  62$  of 
copper  it  may  be  rolled  hot. 

In  cold  rolling  of  brass,  it  takes  but  a  few  passes  through  the 
rolls  to  make  the  metal  very  brittle.  To  relieve  this  brittleness, 
frequent  annealings  are  necessary.  Each  annealing  must  be  fol- 
lowed by  pickling  in  weak  acid  and  thorough  washing  to  prepare  the 
sheet  for  further  rolling. 

Annealing  is  done  in  muffle  furnaces  at  about  700°  F.,  and  the 
metal  is  cooled  by  exposure  to  air,  or  its  cooling  may  be  hastened  by 
sprays  of  water,  if  the  alloy  is  such  as  not  to  be  injured  thereby. 

In  the  manufacture  of  high-grade  sheet  brass,  the  plate  is  sub- 
jected to  a  process  called  "  scalping/7  after  about  the  second  anneal- 
ing. This  process  is  in  lieu  of  pickling  which  would  otherwise  fol- 
low this  annealing.  It  consists  of  placing  the  sheet  on  a  machine 
which  scrapes  the  surfaces  bright  and  clean  by  means  of  a  rapidly 
oscillating  scraper.  Successive  rollings,  annealings  and  picklings 
are  then  given  the  sheet  until  it  is  reduced  to  the  required  thickness. 

If  the  sheet  is  to  be  finished  as  soft  brass,  it  must  be  annealed 
after  the  last  rolling,  and  the  dull  surface  due  to  this  annealing  is 
removed  by  dipping  in  weak  acid,  rinsing,  and  polishing  with  bran. 

Brass  may  be  left  with  different  degrees  of  hardness  and  springi- 
ness by  more  or  less  rolling  after  the  last  annealing  and  not  anneal- 
ing again.  New  hard  brass  always  has  a  shiny  surface. 

173.  Extruded  Brass. — The  process  of  extrusion  produces  brass 
and  bronze  shapes  similar  to  rolled  shapes.     Shapes  of  more  com- 
plicated cross  section  can  be  produced  by  the  extruding  process  than 
by  rolling.     Many  brass  and  bronze  compositions  will  stand  cold 
rolling,  but  will  not  stand  the  extruding  process. 


156 


MECHANICAL  PROCESSES 


Extruding  is  the  process  of  forcing  metal  or  other  substance 
through  a  hole  in  a  block  of  hard  metal,  usually  hard  steel.  This 
block  of  metal  is  called  a  die  and  the  hole  in  it  determines  the  shape 
of  the  cross  section  of  the  substance  forced  through  it. 

Fig.  56  illustrates  the  principal  features  of  the  extruding  press  as 
used  for  brass  and  bronze.  A  round  billet  of  brass  is  cast  of  such 
a  size  as  will  easily  go  in  the  heavy  cast-steel  cylinder  or  container 
A.  The  container  may  be  lifted  or  revolved  so  that  the  billet  can 
be  placed  readily  in  the  open  end  at  the  right.  The  die  D  having 
been  placed  as  shown  in  the  view,  the  red-hot  billet  is  taken  from 
the  reheating  furnace,  is  scraped  or  struck  to  remove  any  clinging 
scale,  and  is  quickly  placed  in  the  container  which  is  at  once  lowered 
to  the  position  shown.  By  means  of  intensified  hydraulic  pressure 


FIG.  56. — Extruding  Press. 

in  the  cylinder  C,  the  ram  P  is  forced  against  the  billet  with 
sufficient  pressure  to  force  the  metal  through  the  hole  in  the  die. 
A  man  stands  with  tongs  ready  to  grasp  the  end  of  the  piece  as  it 
emerges  through  the  die  and  conduct  it  along  the  metal-covered 
table  T,  keeping  the  piece  straight  so  that  it  may  cool  straight.  The 
lower  sketch  shows  the  front  view  of  a  die  such  as  is  used  for  mak- 
ing bronze  deck-beams. 

A  hydraulic  pressure,  several  times  intensified,,  amounting  to 
60,000  Ibs.  per  square  inch  is  sometimes  needed  for  this  work.  The 
weight  of  billets,  limited  by  the  capacity  of  the  container,  does  not 
exceed  175  Ibs.  The  quality  of  the  extruded  bars  is  said  to  be 
better  than  that  of  bars  produced  by  rolling,  and  certainty  the  pres- 
sure leaves  no  blow  holes  and  crowds  the  molecules  of  the  metal 
closely  together.  The  extruding  of  metals,  hot  or  cold,  is  a  matter 
of  the  power  of  the  extruding  press  and  of  the  ductility  of  the 
metal. 


MECHANICAL  AND  HEAT  TREATMENT  OF  METALS 


157 


174.  Extruded  Shapes. — Fig.  57  shows  cross  sections  of  some  of 
the  shapes  produced  by  this  process.  Besides  the  four  shapes  of 
bars  at  the  top  there  are  shown  a  few  special  shapes  as  follows : 


FIG.  57. — Extruded  Shapes. 

A — Fluted  column  for  interior  architectural  work.  E — Moulding. 

B — Hand  railing  for  interior  architectural  work.  F — Angle  bar. 

C — Stair  tread.  G — I-Beam. 
D — Door  sill. 


Extruded  shapes  are  extensively  used  for  high-grade  interior 
architectural  trimming,  as  well  as  for  ornamental  structural  work 
where  strength  is  a  factor.  In  many  cases  the  bars  may  be  cut  in 
short  pieces  and  thus  supply  shapes  which  ordinarily  must  be  pro- 
duced by  casting.  The  extruded  metal  needs  no  further  finishing, 
as  it  has  smooth  and  even  surfaces. 

Lead  pipe  is  produced  by  the  extruding  process. 

11 


CHAPTER  VI. 
THE  RE-MANUFACTURE  OF  METALS. 

175.  Scope  of  Metal  Re-Manufacturing. — This  branch  of  metal 
working  includes  a  great  variety  of  manufacturing  industries  which 
shape  metals  for  final  uses.     In  general,  the  re-manufacture  of 
metals  includes  all  processes  which  start  with  rolling-mill  products, 
such  as  plates,  bars,  rods,  etc.,  and  turn  out  an  endless  variety  of 
metal   articles   which   enter   into   almost   every   range   of   service. 
Possibly  the  most  familiar  branch  of  metal  re-manufacturing  is 
that  in  the  shop  of  the  village  blacksmith.    The  blacksmith  shapes, 
by  manual  labor,  many  articles  from  bars,  rods  and  sheets  of  metal 
which  are  supplied  by  the  rolling  mill. 

By  far  the  greater  part  of  re-manufacturing  is  carried  on  in 
large  workshops  and  factories  in  which  the  main  part  of  the  work  is 
done  by  machines  operated  by  persons  of  more  or  less  skill.  A 
single  manufacturing  establishment  may  be  employed  wholly  in 
making  one  kind  of  article,  wire  for  example,  or  its  range  may  be 
extended  to  making  articles  closely  associated,  as  rivets,  bolts  and 
nuts,  or  automobile  forgings. 

Only  a  few  of  the  re-manufacturing  industries  can  be  given 
particular  mention  here,  and  those  outlined  in  this  chapter  are 
selected  either  to  give  information  of  metal-shaping  methods  which 
produce  well-known  articles,  or  to  show  the  possibilities  of  metal 
Working. 

A  great  many  metal  articles  familiarly  seen  are  products  of  the 
foundry,  where  pigs  of  metal  are  melted  and  cast  into  shape. 
Foundry  products  are  not  usually  classed  as  products  of  re-manu- 
facture, and  will  be  dealt  with  later  on.  They  can  usually  be  readily 
recognized  by  their  more  or  less  irregular  form.  Superficial  in- 
spection will  generally  show  that  they  are  not  made  from  shapes 
supplied  by  the  rolling  mill. 

176.  Tool  Making. — One  of  the  most  important  branches  of  re- 
manufacture  is  that  of  tool  making.    Nearly  all  tools  are  made  of 


THE  KE-MANUFACTUKE  OF  METALS  159 

steel.  Those  used  for  measuring  and  trying,  such  as  calipers,  gages, 
squares  and  scales,  are  sufficiently  hard  and  durable  when  made  of 
low-carbon  steel. 

Tools  for  metal  cutting  are  forged  from  high-carbon  or  alloy- 
crucible  steels  of  the  best  quality.  Carbon  steel  for  tools  is  commonly 
known  as.  machinery  steel. 

A  lasting  keen  edge  on  a  cutting  tool  requires  hardness,  but  hard- 
ness and  brittleness  go  together,  hence  those  tools  which  must  stand 
extreme  shocks,  battering,  twisting,  or  bending,  must  sacrifice  some 
of  the  hardness  to  tenacity  and  ductility. 

Cutting  tools  may  be  forged  or  cast  to  approximate  shape.  The 
rougher  tools  may  be  hardened  and  then  ground  to  finished  shape, 
but  the  tools  for  finer  work,  as  taps  and  dies,  must  be  machined  to 
shape  before  they  are  hardened.  The  process  of  hardening  may  dis- 
tort a  tool  slightly,  which  may  ruin  it  unless  it  can  be  brought  to  its 
true  shape  by  grinding  after  hardening. 

177.  Special  Methods  of  Heating  and  Hardening  Steel  Articles. — 
In  the  older  methods  of  heating,  hardening,  tempering  and  anneal- 
ing steel,  results  depend  entirely  upon  the  eye  and  practice  of  the 
workman.  To  insure  uniform  results,  various  methods  of  heating 
and  hardening  have  been  devised  which  eliminate  judgment,  and 
secure  automatically  the  same  results  in  each  case. 

In  manufacturing  establishments,  tools  and  small  articles  to  be 
hardened  are  usually  heated  in  a  bath  of  red-hot  molten  lead. 
Heating  may  also  be.  done  in  closed  iron  tubes  or  in  small  muffle 
furnaces.  A  pyrometer  must  be  used  to  regulate  the  temperature  of 
a  heating  furnace  or  a  lead  bath. 

To  avoid  burning  off  the  sharp  points  of  file  teeth  and  the  sharp 
cutting  edges  of  threading  dies,  etc.,  during  heating  or  while  trans- 
ferring these  articles  from  the  heating  bath  to  the  quenching  or 
hardening  bath,  the  articles  are  dipped  before  heating  into  a  thin 
hot  paste  of  salt,  flour  and  charred  leather,  or  into  a  hot  salt  solu- 
tion. This  mixture  dries  at  once  and  remains  on  the  surface  until 
after  the  articles  are  hardened. 

For  hardening  steel,  quenching  baths  of  fish  oil,  petroleum 
residue,  or  brine  are  much  used,  and  are  kept  at  constant  and  uni- 
form temperature  by  agitation  or  by  a  constant  flow  from  one 
receptacle  to  another.  These  quenching  baths  are  not  so  sudden 


160  MECHANICAL  PROCESSES 

in  their  cooling  effect  as  is  pure  water,  hence  the  shock  to  the  metal 
is  less,  and  the  degree  of  hardness  given  is  sufficient.  The  con- 
sistency and  temperature  of  a  quenching  bath  is  determined  by  ex- 
periment to  give  the  degree  of  hardness  required  without  further 
process. 

178.  Sheet    Iron. — This   product   is.   familiar   in   many   forms. 
Most  of  the  so-called  sheet  iron  of  to-day  is  sheet  steel  and  not 
wrought  iron  as  it  was  before  the  days  of  mild  steel.     This  sheet 
steel  for  common  uses  is  a  very  soft  grade  of  mild  steel,  very 
pliable  and  easily  worked.    It  is  much  used  by  the  tinsmith  and  is 
the  stock  material  for  the  sheet-metal-shaping  trades  and  manu- 
facturers.   It  is  familiarly  seen  made  up  as  stove  pipes,  steam-pipe 
lagging  protectors,  oil  guards,  etc.,  and  is  either  of  dull  surface 
presenting  faint  waves  of  color  due  to  annealing,  or  is  shiny  black. 

The  dull  black  sheets  may  be  marketed  either  as  such  or  in  the 
following  forms:  (1)  Crimped  into  corrugated  iron,  much  used 
for  covering  warehouses  or  other  buildings;  (2)  coated  with  zinc 
and  known  as  galvanized  iron;  (3)  coated  with  tin  and  known  as 
tin;  and  (4)  planished  with  carbon  and  called  planished  or  Russia 
iron. 

179.  The  Manufacture  of  Sheet  Iron. — Sheet  iron  (as  it  is  com- 
monly known)  is  made  by  rolling  sheet-bar  into  thin  sheets,  as  was 
stated  in  Par.  154. 

At  the  sheet  mill,  the  operation  of  rolling  sheets  is  as  follows: 
The  30-foot  sheet-bars  are  cut  into  short  lengths,  heated  in  a  re- 
heating furnace,  and  run  through  the  rolls  sidewise,  as  the  width 
of  the  bar  is  stretched  out  to  form  the  length  of  the  sheet.  Rolling 
stretches  metal  in  the  direction  of  its  travel  through  the  rolls  and 
very  little  if  at  all  in  the  direction  of  the  axes  of  the  rolls,  hence 
bars  are  cut  into  lengths  but  slightly  longer  than  the  width  of  the 
sheets  to  be  rolled  from  them.  A  mill  similar  to  that  for  rolling 
sheet  brass  and  sheet  copper  is  iised  for  this  work. 

After  about  the  first  five  passes  through  the  roughing  rolls  the 
bar  has  stretched  out  greatly,  is  very  thin,  and  wobbly  while 
hot,  hence,  for  easy  handling  it  is  folded  double,  and  two  thick- 
nesses of  metal  pass  through  the  rolls  at  once.  The  sheets  are  not 
hot  enough  to  weld,  and  their  scale  keeps  them  from  sticking  to- 
gether. This  doubling  is  called  "  matching."  This  doubled  sheet 


THE  RE-MANUFACTURE  OF  METALS  161 

is  then  reheated  with  three  other  matches,  and  all  are  given  one 
pass  through  the  smoothing  rolls  together,  thus  making  six  thick- 
nesses of  metal  in  one  pass.  These  six  sheets  are  allowed  to  cool 
and  are  then  sheared  along  the  ends  and  the  edges,  after  which 
they  are  "  opened  "  or  taken  apart. 

The  sheets  then  go  to  the  cold  rolls  through  which  they  are 
passed  singly  one  or  more  times  to  give  density  and  smoothness, 
after  which  they  are  piled  about  one  hundred  in  a  pile  for  anneal- 
ing. Fig.  58  shows  a  heavy  tray  C  on  which  sheets  are  piled  for 
annealing.  The  cover  T  is  placed  over  the  pile  and  sand  is  placed 
all  around  the  lower  edge  of  the  cover  to  exclude  air.  The  cover 
and  tray  are  lined  with  fire  bricks  and  suitable  lugs  are  fitted  for 
handling  by  the  crane. 


FIG.  58. — Annealing  Tray  for  Sheet  Iron. 

Annealing  requires  about  12  hours.  When  cold,  the  cover  is 
lifted  and  the  sheets  are  stripped  apart  by  hand.  After  inspection, 
they  may  be  bundled  for  market  as  "  dead  soft "  sheets,  or  may  be 
sent  to  other  departments  to  be  corrugated,  tinned,  galvanized  or 
planished. 

If  hard  sheets  are  required  they  are  selected  from  the  colcU 
rolled  stock  before  annealing. 

180.  Galvanizing. — This  consists,  of  covering  articles  of  iron  or 
steel  with  a  coating  of  zinc  for  the  purpose  of  resisting  corrosion. 

Articles  to  be  galvanized  must  first  be  pickled  in  a  dilute  acid 
to  remove  or  loosen  all  surface  dirt  and  scale.  Upon  lifting  from 
this  bath,  the  articles  are  well  brushed  with  brooms  or  steel  brushes 
and  are  washed  with  fresh  water  from  a  hose.  They  are  then 
placed  in  a  second  bath  of  weak  acid  (usually  HC1)  to  insure  a 
clean  metallic  surface  and  must  be  taken  directly  from  this  bath 


162  MECHANICAL  PROCESSES 

to  a  "flux  tank"  to  avoid  rusting,  which  would  occur  if  exposed 
unduly  to  the  air.  The  fluxing  mixture  consists  of  a  solution  of 
sal  ammoniac  kept  hot  by  steam  pipes  and  covered  with  beef  tallow, 
and  is  used  to  neutralize  the  acid  of  the  two  preceding  baths.  From 
the  fluxing  bath  articles  are  lifted  dripping,  and  immediately 
lowered  into  the  galvanizing  bath,  known  as  the  "  zinc  pot."  This 
bath  consists  of  molten  zinc,  which  soon  becomes  covered  with  flux 
and  dross,  and  is  protected  by  these  from  the  oxidizing  action  of 
the  air.  The  zinc  pot  is  an  iron  tank  which  is  surrounded  by  brick 
walls  with  space  enough  between  the  walls  and  the  tank  to  main- 
tain a  coke  fire  for  keeping  the  zinc  melted. 

Small  articles  are  lowered  for  a  moment  into  the  zinc  bath  in 
wire  baskets.  They  are  lifted  out  and  allowed  to  cool. 

The  best  grade  of  galvanized  sheets  is  produced  by  feeding  the 
sheets  taken  directly  from  the  fluxing  bath  into  a  machine  which  is 
submerged  in  the  zinc  pot.  This  machine  is  merely  a  series  of 
rolls  which  draw  the  sheet  into  the  bath,  carry  it  down  near  the 
bottom,  and  finally  send  it  out  over  the  further  edge  of  the  pot. 
These  rolls  insure  an  even  coating  of  zinc  over  the  surface  of  the 
sheet  and  roll  down  all  lumps  and  uneven  places.  Sheets  from  the 
zinc  pot  are  placed  on  edge  in  racks  to  cool,  and  are  then  run 
through  straightening  rolls  and  sorted  to  pick  out  sheets  which  are 
imperfectly  galvanized.  The  imperfect  sheets  are  returned  to  the 
second  acid  bath  if  very  imperfect,  or  are  bundled  and  sold  as 
e<  seconds  "  if  only  slightly  imperfect.  All  sheets  are  branded  be- 
fore bundling  for  market. 

181.  Tinning. — Tinning,  like  galvanizing,  is  a  practical  method 
of  coating  iron  and  steel  to  render  it  non-corrodable.     Tinning 
gives  a  smoother,  brighter  and  better-looking  surface,  and  it  forms 
a  more   durable   coating,   than   does  galvanizing.     Yery   common 
among  tinned  products  are  tinned  wire,  roofing  tin,  tin-lined  cook- 
ing vessels,  and  cans  in  which  preserved  fruits  and  vegetables  are 
held. 

182.  The  Manufacture  of  Tin  Plate. — This  process  is  very  similar 
to  the  process  of  galvanizing,  but  is  more  elaborate,  and  requires 
more  care,  as  the  product  is  used  where  resistance  to  corrosion  is 
more  essential. 


THE  RE-MANUFACTURE  OF  METALS 


163 


Sheets  to  be  tinned  are  rolled  from  sheet-bars  and  are  then 
trimmed  to  measure  14  x  20  inches,  the  standard  size  for  tin  plate. 

After  rolling  and  trimming,  the  sheets  are  selected  with  more 
care  than  for  galvanizing.  They  are  then  pickled  and  rinsed  to 
expose  smooth,  clean  surfaces,  and  are  annealed  on  a  covered  tray. 
Annealing  makes  them  too  pliable  for  use,  hence  each  sheet  is  given 
two  passes  through  finishing  rolls  to  make  the  surfaces  smooth  and 
to  make  the  sheet  springy  or  elastic.  This  annealing  and  rolling 
makes  another  pickling  necessary,  after  which  they  are  kept  under 
water  to  avoid  oxidation  while  waiting  to  go  into  the  tinning  pot. 

The  coat  of  tin  is  applied  by  immersing  one  sheet  at  a  time  in  an 
iron  pot  containing  molten  tin.  The  sheet  enters  the  tin  through 


FIG.  59. — Tinning  Pot. 

a  flux  of  ammonium  chloride  (sal  ammoniac)  which  floats  on  the 
surface  of  the  molten  metal  and  prevents  the  formation  of  dross, 
which  would  cling  to  the  surface  of  the  sheet.  Fig.  59  shows  a  dia- 
gram of  the  upper  part  of  the  tinning  pot,  on  the  back  edge  of 
which  is  mounted  a  grease  pot  G  filled  with  molten  palm  oil,  in 
which  revolve  several  pairs  of  rollers  as  shown.  The  sheet  is 
lifted  from  the  pot  until  gripped  by  the  lowest  pair  of  rolls,  and  it 
is  carried  upward  by  these  and  the  other  rolls  which  deliver  it  to  a 
table  above  the  grease  pot.  The  palm  oil  serves  to  keep  the  plate 
hot  and  to  prevent  oxidation  while  the  rolls  are  pressing  off  super- 
fluous tin  and  smoothing  that  retained  on  the  sheet.  The  slower 
running  of  the  rolls  allows  a  heavier  coating  of  tin  to  stick  to  the 
sheet.  The  tin  in  the  pot  is  kept  molten  by  gas  burners  not  shown. 
After  emerging  from  the  grease  pot,  each  sheet  is  forced  up. 


164  MECHANICAL  PROCESSES 

edge  on,  through  a  bin  of  sawdust  and  lime  to  clean  it,  and  is  then 
passed  through  buffing  and  dusting  rolls,  after  which  it  is  carried 
to  the  sorting  tables.  The  work  of  sorting  is  usually  done  by  girls, 
who  grade  all  sheets  as  "primes"  (1st  grade)  or  "wasters"  (2d 
grade).  Some  "wasters"  having  no  defects  except  a  few  poorly 
tinned  spots  may  be  "mended"  by  cleaning  and  retinning,  thus 
making  "  primes,"  but  "  wasters "  with  bad  defects  must  either 
be  sold  as  seconds  or  x  thrown  out  entirely  for  remelting  and  re- 
covering the  tin. 

Tin  plates  are  usually  packed  112  sheets  to  the  box. 

183.  Terne  Plates. — This  is  a  grade  of  tin  plate  used  for  roofing. 
Terne  plates  are  slightly  heavier  than  tin  plates  and  are  much 
cheaper,  as  they  are  covered  with  a  mixture  of  about  25$  tin  and 
7'5$  cent  lead.    Many  tin  vessels,  not  intended  for  food  receptacles, 
are  made  of  terne  plates. 

184.  Russia  Iron. — This  name  is  applied  to  sheet  iron  of  very 
highly  polished  or  glazed  surface  also  known  as  planished  iron. 

Mt  is  used  for  protecting  the  lagging  of  engines  and  boilers  and  for 
other  uses  where  a  non-corroding  black  iron  of  finished  surface  is 
desired. 

These  sheets  are  made  by  piling  together  about  fifty  pickled  sheets 
of  soft  steel  with  powdered  charcoal  sprinkled  between  adjacent 
sheets.  The  pile  is  wrapped  in  old  sheets,  wired  and  heated  in  a 
furnace  to  a  cherry-red  heat  for  about  6  hours.  Upon  cooling,  each 
sheet  is  swept  free  of  loose  charcoal  and  is  then  sprayed  with  steam 
to  form  a  thin  oxide.  Again  the  sheets  are  piled  together,  heated 
and  then  placed  on  the  hammer  table,  several  in  a  bundle,  and 
pounded  with  a  steam  hammer.  This  brings  about  a  grinding 
action  which  grinds  the  carbon  and  oxide  on  the  surface  down  to  a 
highly  polished  coating. 

185.  Wire  Drawing. — Metals  to  be  made  into  wire  are  first  cast 
(or  rolled  in  the  case  of  wrought  iron)  into  long  square  billets.    A 
billet  intended  for  wire  is  about  4  x  4  x  56  inches.     Brass  and 
copper  billets  are  also  called  "wire  bar,"  when  cast  for  making 
wire. 

The  first  operation  is  to  break  down  these  billets  in  billet  and 
rod  mills.  A  billet  is  run  hot  through  a  continuous  mill  of  about 
eight  sets  of  rolls,  which  break  it  down  to  about  1%-inch  square 


THE  RE-MANUFACTURE  OF  METALS 


165 


cross  section.  It  then  goes  at  once  through  the  looping  rod-mill 
which  delivers  it  as  coiled  rod  varying  from  3/16  to  %  inches 
diameter,  and  a  hundred  or  more  feet  in  length. 

These  coils  are  sent  to  the  wire  mills  and  the  remainder  of  the 
process  of  reducing  them  to  the  diameter  of  wire  required  is  ac- 
complished by  drawing  them  cold  through  dies. 

At  the  wire  mill,  coils  must  first  be  pickled  to  remove  all  scale. 
After  this  they  are  dipped  in  lime  water  and  dried  in  a  steam- 
drying  room  where  they  remain  until  removed  to  be  drawn. 

Fig.  60  shows  in  cross  section  a  steel  die  for  wire  drawing.  The 
work  of  drawing  is  done  on  the  draw  bench,  as  shown  in  Fig.  61, 


FIG.  60. 

Wire 
Drawing 

Die. 


FIG.  61. — Wire-Drawing  Bencn. 


which  is  a  long  bench  against  the  shop  wall.  Along  this  bench 
are-  mounted,  on  vertical  spindles,  a  row  of  short  cylindrical  drums 
about  22  inches  in  diameter.  These  drums,  known  as  "  drawing 
blocks,"  are  made  to  revolve  by  being  geared  to  a  long  shaft  under 
the  bench.  A  drum  resembles  somewhat  a  car  wheel,  with  the 
flange  at  its  lower  edge,  and  each  drum  may  be  stopped  at  will 
while  the  remainder  on  the  bench  continue  in  motion.  Near  each 
drum,  at  the  edge  of  the  bench,  is  a  small  vise,  or  "  frame,"  which 
holds  the  die. 

A  coil  of  rod  from  the  drying  room  is  placed  on  a  reel  fastened  to 
the  floor  near  each  frame  on  the  draw  bench,  and  a  rod  end  is  filed 


166  MECHANICAL  PROCESSES 

or  hammered  so  that  it  will  pass  through  the  die.  An  appliance  on 
the  bench  pulls  about  6  feet  of  this  end  through  the  die.  A  work- 
man fastens  this  end  to  the  drawing  block  and  starts  the  block  in 
motion.  The  revolutions  of  the  block  draw  the  rod  through  the  die 
and  the  wire  is  wound  on  the  block,  which  continues  in  motion 
until  the  entire  rod  is  drawn  through. 

The  percentage  of  reduction  in  diameter  accomplished  by  the  die 
depends  upon  the  softness  of  the  rod.  Drawing  must  necessarily 
pull  a  metal  beyond  its  elastic  limit,  else  the  metal  would  not  re- 
main in  the  shape  drawn,  but  the  metal  cannot  be  pulled  too  near 
its  tensile  strength,  else  it  would  break. 

After  one  or  more  drawings,  the  coil  must  be  taken  from  the 
block  and  annealed  to  soften  it  and  relieve  it  of  brittleness.  To 
prevent  scale  forming  on  the  wire  in  annealing,  several  coils  are 
placed  in  an  annealing  pot  which  is  sealed  and  heated  in  the  an- 
nealing furnace.  Successive  drawings  and  annealings  are  con- 
tinued until  the  wire  is  reduced  to  the  diameter  required. 

Manufacturers  lubricate  wire  dies  with  oil,  solid  grease  or  a  fer- 
ment of  bran  and  yeast  in  water.  Common  wire  is  made  usually 
of  acid  Bessemer  steel.  Sounding  wire,  piano  wire  and  other  high- 
grade  wires  are  made  of  crucible  steel  or  of  open-hearth  steel  re- 
fined in  the  electric  furnace. 

186.  Gaging  the  Sizes  of  Wire. — For  designating  the  diameters 
of  wire,  thicknesses  of  sheet  metals,  and  thicknesses  of  the  walls  of 
tubes,  various  arbitrarily  chosen  scales  of  sizes  are  used  in  America 
and  in  Europe.  These  sizes  are  designated  as  wire-gage  units. 
For  example,  a  wire  may  be  designated  as  No.  5,  B.  &  S.  (Brown  & 
Sharpe)  or  No.  5,  B.  W.  G.  (Birmingham  Wire  Gage). 

The  several  systems  use  numbers  to  designate  sizes  ranging  from 
0000000  (usually  expressed  as  7/0)  to  50,  although  the  sizes  are  of 
different  dimensions  in  the  different  systems.* 

In  America  the  B.  &  S.  gage  (prepared  by  Messrs.  Brown  & 
Sharpe  Mfg.  Co.,  Providence,  E.  I.)  is  standard  among  manufac- 
turers for  designating  wire  sizes  and  metal  thicknesses,  although 
the  U.  S.  Navy  Department  has  adopted  the  B.  W.  G.  (Birmingham 

*  A  table  in  the  Appendix  gives  a  comparison  of  the  different  wire- 
gage  systems. 


THE  RE-MANUFACTURE  OF  METALS  167 

Wire  Gage)  for  designating  thickness  of  walls  of  pipes  and  tubes, 
and  the  U.  S.  standard  gage  for  designating  steel  and  iron-plate 
thicknesses. 

The  finest  wire  drawn  is  a  copper  wire  of  about  .001-inch 
diameter. 

187.  Coating  Wire  for  Protection  from  Corrosion.— Most  of  the 
iron  wire  of  to-day  is  made  of  low-carbon  steel,  which  corrodes  very 
quickly.    The  cheapest  protection  is  galvanizing,  though  tinned  or 
coppered  wires  are  more  effectively  protected. 

Galvanizing  and  tinning  are  done  by  passing  wire  from  one  reel 
to  another  first  through  a  bath  of  weak  hydrochloric  acid  to  clean 
it,  then  through  a  wiper  of  waste.  It  is  then  pulled  under  suitable 
guides  through  a  bath  of  molten  zinc  or  tin,  according  to  whether 
the  process  is  galvanizing  or  tinning,  and  from  this  bath  it  passes 
through  a  wiper  of  asbestos  fiber  to  remove  lumps  of  the  coating 
material  before  it  cools  and  is  wound  into  a  coil. 

Pickled  wire  coils  dipped  into  copper-sulphate  solution  take  a 
coating  of  copper,  and  when  drawn  the  wire  has  a  bright  copper 
surface. 

188.  Hard  Wire.     Spring  Material. — Drawing  hardens  wire  and 
the  hardness  differs  in  degree  according  to  the  composition  of  the 
wire  and  the  amount  of  reduction  without  annealing.     Wire  which 
is  not  annealed  after  drawing  is  called  "bench-hardened"  wire. 
Steel  wire  containing  as  high  as  1.20$  per  cent  of  carbon  is  drawn 
cold,  and  this  may,  if  desired,  be  made  harder  just  as  steel  tools 
are  hardened.     High-carbon  steel  wire  is  generally  marketed  in 
straight  lengths  of  a  few  feet,  annealed,  and  it  is  hardened  as  may 
be  desired  by  the  user. 

Flat  wire  or  ribbon  wire,  containing  about  .9$  of  carbon,  such 
as  is  used  for  clock  and  watch  springs,  is  drawn  the  same  as  round 
wire,  though  the  large  sizes  for  coiled  springs  must  be  rolled.  This 
material  is  hardened  and  tempered  while  winding  it  from  one  reel 
to  another.  It  passes  through  an  oil  flame  to  heat  it  to  redness, 
then  through  cold  fish  oil  to  harden  it,  and  last  through  molten 
lead,  kept  at  a  fixed  temperature  by  oil  burners,  to  anneal  it.  The 
hardness  cannot  be  such  that  the  material  will  snap  if  rolled  into 
coils. 


168  MECHANICAL  PROCESSES 

Wire  is  very  soft  and  pliable  if  thoroughly  annealed  after 
drawing. 

189.  Pipes  and  Tubes. — These  two  words  are  much  confused  in 
their  applications.     Commercially,  there  are  many  kinds  of  pipes 
and  tubes  of  many  sizes  and  materials. 

The  pipe  and  tube-making  processes  described  in  the  following 
paragraphs  embody  the  essential  principles  of  making  pipes  and 
tubes  of  all  kinds  in  which  ductile  metals  are  used. 

Cast-iron  pipes  are  much  used  for  large  water,  oil  and  gas  mains. 
These  are  products  of  the  foundry  and  will  not  be  described  here. 

All  pipes  and  tubes  made  of  wrought  iron  or  mild  steel  are 
manufactured  by  one  of  two  general  processes;  either  by  shaping 
metal  strips  called  "  skelp  "  into  cylindrical  form  and  welding  the 
edges  together;  or  by  drawing  the  tubes  from  solid  billets  or  flat 
plates.  The  products  of  these  two  processes  are  classed  respectively 
as  welded  or  seamless. 

190.  The  Manufacture  of  Welded  Pipe. — Most  of  the  welded  pipe 
is  now  made  of  a  low-carbon  acid  Bessemer  steel.     This  steel  will 
weld  readily,  and  it  has  nearly  displaced  wrought  iron  for  this  use. 

Billets  are  rolled  into  skelp  (which  is  similar  to  sheet-bar)  of  the 
width  and  thickness  required  for  the  pipe.  Each  strip  of  rolled 
skelp  is  cut  into  lengths  of  about  20  feet,  and  each  length  is  made 
into  a  pipe. 

Welded  pipe  is  made  either  by  lap  or  butt  welding  of  skelp 
strips.  Pipes  of  1*4  inches  diameter  and  under  are  butt  welded, 
as  shown  in  Fig.  62  and  those  over  11/4  inches  diameter  are  lap 
welded  as  shown  in  Fig.  63. 

The  methods  of  welding  are  as  follows,  viz. : 

For  Butt  Welds. — In  a  long  flat-bottomed  heating  furnace  with  a 
door  at  one  end  for  receiving  strips  and  a  door  at  the  other  end  for 
removing  them,  a  number  of  strips  are  kept  side  by  side  at  various 
degrees  of  heat  up  to  welding  heat.  When  a  strip  has  reached  weld- 
ing heat,  a  man  reaches  in  at  the  removing  door  with  a  long  pair  of 
tongs  and  curls  over  the  edges  for  a  few  inches  along  the  end  of 
the  strip.  Working  quickly,  he  pulls  the  end  from  the  furnace, 


THE  KE-MANUFACTURE  OF  METALS 


169 


points  it  through  a  tapered  ring  known  as  a  bell  (B,  Fig.  64)  and 
grips  this  end  with  the  nippers  R.  Just  the  instant  the  nippers 
grip  the  strip,  the  hook  H  is  caught  by  a  moving  endless  chain 
under  the  bench  and  the  strip  is  pulled  through  the  bell.  The  bell 
is  so  shaped  that  it  rolls  the  strip  into  cylindrical  form  and  forces 


FIG.  62.  FIG.  63. 

Butt  and  Lap-Welded  Pipe  Joints. 

the  edges  together  firmly  enough  to  make  the  weld.  The  bell  rests 
against  a  shoulder  8  on  the  bench  while  the  strip  is  passing  through, 
but  when  through,  the  bell  falls  into  a  basin  of  cooling  water  and 
another  bell  is  held  in  place  by  tongs  ready  for  another  strip  to 
start  through. 


FIG.  64. — Equipment  for  Making  Butt-Welded  Pipe. 

For  Lap  Welds. — The  shaping  and  the  welding  are  accomplished 
in  two  heatings.  The  first  heating  is  merely  a  red  heat  for  shaping 
the  strip  into  cylindrical  form,  a  process  similar  to  that  for  butt 
welding.  The  second  heating  is  for  welding  the  pipe. 

It  is  apparent  that  the  bell  of  Fig.  64  will  not  bring  the  lap 
firmly  together  for  a  lap  weld,  hence  after  the  pipe  has  been  given 
a  cylindrical  shape,  it  is  reheated  to  welding  heat  in  another  fur- 


170 


MECHANICAL  PROCESSES 


nace  and  run  through  the  welding  rolls  RE,  Fig.  65.     A  view  of 
the  actual  machine  is  shown  in  Fig.  G6.    The  rolls  are  two  grooved 


FIG.  65. — Rolls  and  Mandrel  for  Making  Lap-Welded  Pipe. 


wheels  which  press  the  lapped  edges  together  against  a  mandrel  M 
placed  in  the  end  of  the  pipe  as  it  enters  the  rolls.  The  mandrel 
is  held  directly  between  the  two  rolls  by  the  long  rod  8.  The  pres- 


FIG.  66.— Machine  for  Lap-Welding  Pipe. 

sure  of  the  rolls  forces  the  pipe  against  this  mandrel  and  makes 
the  weld. 

After  welding,  both  butt  and  lap-welded  pipes  are  run  cold  through 
sizing  rolls,,  which  gives  them  correct  outside  diameter,  and  through 


THE  KE-MANUFACTURE  OF  METALS  171 

cross  rolls,  which  straighten  them  and  give  the  surface  a  clean 
finish.  The  pipes  then  go  to  the  inspection  table,  ends  are  sawed 
off,  and  the  short  pieces  are  crushed  cold  to  show  the  effectiveness 
of  the  weld.  The  pipe  is  carefully  inspected  outside,  is  tested  by 
hydraulic  pressure  of  at  least  600  Ibs.  per  square  inch,  and,  if 
passed,  it  is  annealed  to  reduce  the  size  of  the  crystals  and  increase 
the  elasticity. 

Pipes  are  threaded  on  the  ends  after  annealing  and  are  then 
ready  to  be  made  up  in  bundles  for  shipping.  Each  length  of  pipe 
is  shipped  with  a  short  threaded  sleeve  called  a  coupling  screwed 
on  one  end  of  the  pipe.  This  is  used  in  joining  lengths  of  pipe 
together.  Some  grades  of  boiler  tubes  are  produced  by  the  lap- 
welding  process. 

191.  Defects  in  Welded  Pipe. — Besides  defective  welds,  the  fol- 
lowing named  defects  in  welded  pipes,  with  their  causes,  may  be 
mentioned : 

(1)  Cracks  or  Seams. — These  originate  in  the  ingot  as  blow 
holes,  shrinkage,  cracks  or  other  defects.   An  ingot  defect  lengthens 
out  when  the  material  is  rolled  into  skelp. 

(2)  Blisters. — These  are  caused  by  piping  in  the  ingot.     Heat 
swells  them  above  the  surface  of  the  skelp. 

(3)  Scale  Pits  and  Sand  Marks. — These  are  small  indentations 
caused  by  rolling  scale  or  sand  into  the  surfaces  of  the  skelp. 

192.  Iron  Pipe. — Welded  pipe  is  commonly  seen  and  much  used 
as  steam,  gas  and  water  pipe,  and  is  commercially  known  as  iron  pipe. 
It  is  made  in  standard  sizes  designated  in  inches  as  follows,  viz. : 
%,  a/4,  %,  y2,  3/4,  1,  1%,  iy2,  2,  2V,,  3,  31/3,  4,  41/2,  and  in  sizes  of 
even  inches  from  5  to  12,  both  inclusive.    These  sizes  refer  to  the 
inside  diameters  of  the  pipe,  but,  as  a  matter  of  fact  they  are  only 
nominal,  as  the  actual  diameters  differ  more  or  less  from  the  desig- 
nated diameters.    While  iron  pipe  is  referred  to  by  its  nominal  inside 
diameter,  it  is  standardized  in  size  in  outside  diameters.* 

Iron  pipe  is  marketed  either  galvanized  or  plain,  and  some  makers 
coat  pipe  with  asphalt  or  tar. 

For  very  heavy  pressures,  or  for  driving  oil  or  artesian  wells,  two 
special  thicknesses  of  iron  pipe  are  made,  known  commercially  as 

*  Paragraph  437  of  the  Appendix  gives  a  table  of  sizes  and  dimen- 
sions of  standard  iron  pipe. 


172  MECHANICAL  PROCESSES 

extra  strong  and  double  extra  strong.  These  have  the  same  ex- 
ternal diameters  as  the  standard  piping.  Also,  iron  pipe  is  made 
much  larger  than  12  inches  in  diameter  for  many  uses. 

Iron  pipe  is  much  used  as  underground  conduits  for  electric  wires. 
193.  Seamless  Tubes. — It  is  not  commercially  practicable  to  pro- 
duce a  welded  tube  which  shall  uniformly  have  the  same  strength 
at  the  weld  as  in  other  parts  of  the  metal.  The  temperature  to 
which  it  is  necessary  to  heat  the  metal  for  welding  is  such  that  the 
material  may  be  burned  to  a  greater  or  less  extent,  a  condition 
which  it  is  not  always  possible  to  detect. 

For  these  reasons,  boiler  tubes  and  other  tubes  or  pipes  which 
must  stand  high  pressures  and  which  are  subjected  to  great  varia- 
tions of  temperature,  are  preferably  made  without  welds  or  seams. 
There  are  several  methods  for  producing  seamless  tubes  which 
are  applied  to  various  materials,  including  steels  of  practically  all 
compositions,  brass,  copper,  etc.  The  method  of  making  seamless 
tubes  in  general  use  consists  in  piercing  a  hole  axially  through  a 
billet  of  circular  cross  section,  reducing  the  wall  thickness  of  the 
tube  so  produced  by  rolling,  and  finishing,  when  the  conditions 
require,  by  further  reducing  the  wall .  thickness  by  cold  drawing. 
Some  compositions  of  brass  will  not  stand  piercing,  hence  tube 
billets  of  these  compositions  are  cast  hollow  and  reduced  in  size  by 
drawing. 

194.  Piercing  Billets  for  Seamless  Tubes. — This  first  operation 
in  making  seamless  steel  tubes  begins  with  small  ingots  supplied 
by  the  rolling  mill,  free  from  surface  flaws.  These  ingots  are 
heated  and  rolled  into  cylindrical  form,  and  are  sawed  hot  into 
lengths  required.  Each  of  these  lengths,  called  a  blank,  may  range 
in  weight  from  40  to  1000  Ibs.,  according  to  the  size  of  tube  to 
be  made. 

When  cold,  a  hole  about  %-inch  diameter  and  %-inch  deep  is 
drilled  in  the  center  of  one  end  of  each  blank,  and  the  blanks  are 
then  reheated  to  about  2200°  F.  for  piercing. 

The  reheating  furnace  may  be  any  of  the  various  types  used  for 
heating  billets.  The  bed  of  the  furnace  is  usually  inclined  so  that 
blanks  may  gradually  roll  in  a  continuous  line  one  against  another 
through  the  furnace. 


THE  RE-MANUFACTURE  OF  METALS 


173 


From  the  furnace,  each  hot  blank  is  taken  directly  to  the  piercing 
mill,  the  principle  of  which  is  shown  in  Fig.  67.  This  is  the 
Stiefel  mill,  and  is  used  more  than  other  mills  in  this  work.  The 
principle  of  operation  is  the  same  in  all  piercing  mills,  and  they 
vary  only  in  their  mechanism. 

The  discs  A  and  B,  beveled  alike  on  the  faces,  revolve  in  the 
same  direction,  and  their  axes  X  and  Y  are  parallel.  The  blank  K 
is  supported  in  a  trough  so  placed  that  its  axis,  DD,  makes  equal 
angles  with  the  face  C  and  with  the  bevel  F  of  the  two  discs;  also 
the  axis  DD  is  in  the  same  plane  which  contains  the  axes  X  and  Y 
of  the  discs. 


FIG.  67. — Making  Seamless  Tubes.     Piercing  Rolls. 

The  blank  is  pushed  by  a  bar  in  the  hands  of  workmen  until 
gripped  by  the  discs,  which  take  hold  of  it,  giving  it  a  rotary 
motion  and  forcing  it  against  the  piercing  mandrel  P,  a  conical 
piece  of  cast  steel  held  in  place  by  the  piercing  bar  R.  The  pier- 
cing mandrel  is  made  to  start  centrally  by  the  small  hole  drilled  in 
one  end  of  the  blank,  and  the  piercing  bar  is  held  to  its  place  by  a 
thrust  bearing  which  allows  it  to  revolve  freely.  The  motion  of  the 
discs  gives  the  blank  a  motion  of  translation  in  the  direction  of  its 
axis,  besides  the  rotary  motion.  This  forces  the  blank  entirely 
over  the  piercing  mandrel  in  a  few  seconds,  and  the  operation  of 
piercing  lengthens  the  blank  into  a  tube  from  two  to  four  times  the 
length  of  the  blank. 
12 


174 


MECHANICAL  PROCESSES 


This  tube  is  in  a  rough  state  after  piercing,  not  -uniform  in 
diameter  and  with  a  surface  somewhat  wavy.  The  original  process 
of  piercing  tubes,,  invented  by  the  Messrs.  Mannesmann  gave  the 
pierced  blank  a  spiral  twist.  This  was  found  to  be  a  disadvantage, 
giving  an  unnecessary  strain  to  the  metal  of  the  tube  walls,  and  the 
Steifel  process  is  among  those  devised  to  reduce  this  fault. 

To  smooth  the  tube  up  and  give  it  uniform  diameter,  it  is  sub- 
jected to  five  finishing  operations,  with  or  without  reheating,  ac- 
cording to  the  size  of  the  tube.  These  operations  are : 


FIG.  68. — Making  Seamless  Tubes.     Tube  Rolls. 

(1)  Rolling  the  pierced  blank  to  give  uniform  diameters  and 
thickness  of  wall. 

(2)  Cross   rolling,   to   remove   scratches   and   smooth   the   tube 
surface. 

(3)  Sizing,  to  reduce  the  tube  to  a  specified  diameter. 

(4)  Straightening. 

(5)  Cutting  to  length. 

195.  Rolling  Pierced  Blanks. — This  operation  is  done  by  two 
grooved  rolls.  Fig.  68  shows  a  plan  view  of  this  machine  with  the 
upper  roll  removed. 


THE  KE-MANUFACTURE  OF  METALS 


175 


These  rolls  force  the  tube  over  a  fixed  mandrel  A  supported  be- 
tween the  rolls  by  a  bar  B.  The  bar  is  supported  by  a  yoke  C. 
Several  passes  through  the  rolls  over  the  mandrel  A  reduce  the 
tube  wall  to  the  thickness  desired,  and  give  uniform  diameters. 
The  size  of  the  mandrel  and  of  the  roll  passes  determine  the  thick- 
ness and  diameters  of  the  tube.  This  operation  leaves  scratches 
inside  the  tube  which  are  removed  in  the  next  operation. 

196.  Cross  Rolling. — This  work  is  done  in  a  reeling  machine, 
the  principle  of  which  is  shown  in  Fig.  69. 


ii 


FIG.  69. — Making  Seamless  Tubes.     Tube  Reeling  Machine. 

Supposing  the  axis  of  the  tube  to  lie  in  the  plane  of  the  page, 
the  axis  of  the  upper  roll  is  inclined  downward  toward  the  right, 
and  that  of  the  lower  roll  is  inclined  downward  toward  the  left. 
The  revolutions  of  the  rolls  inclined  in  this  way  not  only  revolve 
the  tube,  but  push  it  forward  over  the  mandrel  M.  The  mandrel 
is  supported  by  its  bar  It,  and  is  free  to  revolve  with  the  tube.  This 
operation  may  change  the  tube  diameter  somewhat. 

197.  Sizing. — This  is  done  by  a  small  two-high  rolling  mill  the 
rolls  of  which  have  circular  passes  of  two  sizes.  The  first  pass 
reduces  the  tube  to  within  1/32  of  an  inch  of  the  finished  diameter 
and  the  second  pass  reduces  it  to  finished  diameter  plus  a  small 
amount  which  the  diameter  will  contract  in  cooling,  as  the  tube  is 
no-w  at  a  dull  red  heat. 


176 


MECHANICAL  PROCESSES 


198.  Straightening  and  Cutting  to  Length. — After  sizing,  the 
tube  is  transferred  to  a  machine  which  consists  essentially  of  a  pair 
of  cross  rolls  as  shown  in  Fig.  70.  The  axes  of  these  rolls,  BC  and 
DGr,  are  inclined  at  equal  angles  on  each  side  of  the  tube  axis  KL. 
The  tube  is  pushed  through  in  the  direction  of  its  length  between 
the  two  rolls,  which  revolve  in  the  same  direction. 

The  arrangement  of  these  rolls  is  identical  with  that  in  the 
reeling  machine.  They  are  much  longer  than  the  reeling  rolls. 
Their  surfaces  are  hyperboloids  of  revolution  and  each  face  is 
generated  by  a  straight  line  K'L'  revolving  about  an  axis  B'C'  at 
a  fixed  distance  08  from  it.  The  two  rolls  are  so  inclined  that  the 


FIG.  70. — Rolls  for  Straightening  Tubes. 

contact  of  the  tube  with  the  rolls  approximates  a  generating  element 
as  near  as  possible. 

Suitable  guides  prevent  the  tube  from  taking  any  lateral  move- 
ment. 

From  the  straightening  rolls,  the  tube  is  sent  to  the  cooling 
table,  down  which  it  rolls  gradually,  against  other  tubes,  to  keep  it 
straight  as  it  cools. 

The  hot  work  on  the  tube  is  now  complete,  and  without  further 
operation  than  cutting  to  length  and  testing,  these  tubes  are  suit- 
able for  use  as  boiler  tubes  or  for  many  mechanical  and  structural 
purposes. 

After  cutting  to  length  in  a  simple  cutting  machine,  each  tube  is 
tested  to  an  internal  hydrostatic  pressure  of  1000  Ibs.  per  square 
inch,  is  carefully  inspected  and  marked. 


THE  BE-MANUFACTURE  OF  METALS 


177 


FIG.  71. — Three  Views  of  a  Cold-Draw  Bench. 


178 


MECHANICAL  PROCESSES 


Annealing  is  not  necessary,  as  the  increase  in  its  grain  size  is 
reduced  by  the  constant  working  of  the  material  after  it  left  the 
furnace. 

199.  Cold-Drawn  Tubes. — Tubes  can  be  produced  from  2  to  6 
inches  outside  diameter  by  the  hot  finishing  process.  When  neces- 
sary to  produce  (1)  tubes  of  less  than  2  inches  diameter,  or  (2) 
larger  tubes  requiring  the  smoothest  surfaces,  or  (3)  tubes  requir- 
ing greater  accuracy  in  diameter  and  thickness  of  wall  than  can 
be  produced  by  the  hot  process,  this  process  must  be  followed  by  a 
series  of  cold  drawing  operations. 


FIG.  72. — The  Operation  of  Cold-Drawing  Tubes. 

These  operations  consist  of  drawing  the  hot-rolled  tube  through 
dies  and  over  mandrels  to  reduce  its  diameters  and  thickness  of 
wall. 

The  various  steps  in  the  cold  drawing  operations  may  be  de- 
scribed as  follows :  The  hot-rolled  tube,  after  having  cooled,  is 
heated  at  one  end  and  forged  down  to  a  rough  point  or  tag,  as 
shown  at  PI,  Fig.  72.  After  pointing,  the  tube  is  cleaned  of  dirt 
and  scale  by  pickling  in  hot  dilute  sulphuric  acid.  It  is  washed  in 
an  alkali  water  to  remove  all  traces  of  acid,  and  is  then  immersed 
in  a  lubricating  vat.  The  lubricant  consists  of  flour,  water  and 
tallow.  After  lubricating,  the  tube  is  taken  to  the  cold-draw  bench 
shown  in  the  lower  sketch  of  Fig.  72.* 

*  Fig.  71  shows  three  views  of  a  cold-draw  bench  in  the  shop. 


THE  EE-MANUFACTURE  OF  METALS  179 

This  machine  consists  of  a  frame  arranged  with  a  support  for  a 
die  D,  and  is  provided  with  a  traveling  chain  or  other  means  of 
moving  a  gripper  or  plier  G  away  from  the  die.  The  other  end  of 
the  machine  forms  a  support  for  the  end  of  the  mandrel  rod  B. 
A  die  shown  in  cross  section  at  DD  of  the  upper  view  is  placed  in 
the  die  support.  The  pointed  end  of  the  tube  is  then  pushed 
through  the  opening  in  the  die  and  a  cylindrical  mandrel  M  on  the 
end  of  the  rod  B  is  entered  into  the  tube.  A  head  C  formed  on  the 
rod  B  engages  with  the  frame  of  the  bench,  so  that  the  mandrel  and 
die  are  held  rigidly  in  proper  relation  to  each  other  as  shown  in  the 
figure. 

The  opening  in  the  die  is  smaller  by  from  %  inch  to  y2  inch 
than  the  diameter  of  the  tube  operated  upon.  The  mandrel  M  is 
also  smaller  than  the  inside  diameter  of  the  tube,  but  to  a  slightly 
less  degree  than  the  die,  so  that  the  difference  between  the  die  and 
the  mandrel  size  is  less  than  the  difference  between  the  outside  and 
inside  diameters  of  the  tube  operated  upon.  The  result  is  that  in 
passing  the  tube  through  the  die  and  over  the  mandrel,  the  diameter 
and  wall  thickness  are  simultaneously  reduced. 

The  point  of  the  tube  having  been  placed  through  the  die  with 
the  mandrel  M  in  position,  is  gripped  by  the  gripper  Cr,  which  in  turn 
is  engaged  by  a  hook  with  a  moving  chain  /.  The  tube  is  pulled 
through  the  die  and  over  the  mandrel  at  the  speed  of  the  gripper.  By 
this  means,  the  sectional  area  of  the  tube  is  reduced  about  15%  for 
small  tubes  of  light  wall  and  up  to  25%  or  to  the  strength  of  the 
bench  for  larger  sizes.  The  drawing  operation  is  repeated  from  2 
to  10  times  until  the  desired  diameter  and  wall  thickness  are  ob- 
tained. 

After  each  cold-drawing  operation  it  is  necessary  to  anneal  the 
tube  in  order  to  soften  it  for  the  succeeding,  cold  drawing.  After 
annealing,  the  tube  is  pickled  and  lubricated  as  before.  For  many 
purposes  the  cold-drawn  tube  is  used  without  annealing;  but  for 
purposes  which  require  ductility  in  the  material  the  tube  is  annealed 
at  various  degrees  corresponding  to  the  physical  properties  required. 
A  temperature  of  1200°  F.  removes  all  traces  of  the  effect  of  cold 
drawing. 

After  receiving  final  operation,  the  tube  is  transferred  to  the 
finishing  department  where  it  is  straightened  and  cut  to  length, 
inspected,  gaged  and  tested  and  is  then  ready  for  shipment. 


180 


MECHANICAL  PROCESSES 


200.  Brass  and  Copper  Tubing. — The  same  methods  of  piercing 
and  cold  drawing  described  for  making  steel  tubes  are  used  to  make 
tubes  of  copper  and  brass.  Billets  of  brass  are  sometimes  turned  in 
a  lathe  to  remove  the  rough  outer  surface  before  piercing. 


FIG.  73. — Mannesmann  Piercing  Rolls. 

Fig.  73  shows  plan  and  side  views,  partly  in  section,  of  a  pair  of 
Mannesmann  rolls  much  used  for  piercing  billets  of  copper  and 
brass. 

Brass  pipe  cannot  be  made  by  welding.  It  is  made  by  piercing 
(or  casting  hollow)  and  then  cold  drawing.  It  is  usually  sent  from 
the  factory  partially  softened  by  annealing  after  drawing. 


THE  KE-MAXUFACTURE  OF  METALS  181 

201.  Tubes  of  Thin  Walls  and  Small  Diameters. — A  tube  may  be 
cold  drawn  over  a  mandrel,  as  previously  described,  until  its  wall 
is  too  thin  to  stand  further  pulling  through  the  die.  If  the  tube 
wall  is  to  be  made  thinner,  further  drawing  is  done  by  placing  the 
tube  over  a  solid  steel  arbor  and  drawing  it  down  as  shown  in  Fig. 
74.  The  tension  of  drawing  is  then  taken  by  the  arbor  and  the  tube 
wall  may  be  drawn  very  thin.  Large  rigid  arbors  are  pushed 
through  the  die.  When  the  drawing  is  done,  the  tube  is  removed 
from  the  arbor  by  hammering  it  gently  with  a  wooden  mallet  or  by 
passing  it  between  rolls. 

Very  small  tubes  are  made  without  a  mandrel.  They  are  first 
cold  drawn  over  a  mandrel  to  a  diameter  of  %  inch  or  less  and  are 
then  "  sunk "  by  drawing  through  the  die  without  a  mandrel. 


FIG.  74. — Arbor  for  Drawing  Thin  Tubes. 

This  reduces  inside  and  outside  diameters,  but  increases  the  thick- 
ness of  wall.    If  the  wall  is  to  be  very  thin,  an  arbor  is  placed  in 
the  tube  after  it  has  been  sunk  nearly  to  the  required  inside  diameter 
and  the  wall  may  then  be  drawn  down  as  thin  as  required. 
202.  Defects  in  Seamless  Tubes. 

(1)  Snakes   are   small   surface  cracks   developed  from   surface 
cracks  of  the  ingot.     They  are  elongated  in  rolling,  and  are  very 
small  and  hard  to  detect.    They  are  more  common  in  rolled  plates 
than  in  tubes. 

(2)  Laps  are  thin  fins  of  metal  stretched  and  folded  over  the 
adjacent  metal  of  the  tube.    They  are  caused  in  piercing. 

(3)  Pits  are  small  depressions  caused  by  over  pickling  or  by 
rolling  sand  or  scale  into  the  tube  surface*. 

(4)  Slivers  are  tongue-shaped  pieces  of  metal  developed  from 
blow  holes  or  shrinkage  cracks  in  the  ingot. 


182 


MECHANICAL  PROCESSES 


(5)  Tears  are  ragged 'openings  in  the  tube  surface  caused  inside 
by  metal  not  passing  freely  over  the  mandrel  at  the  draw  bench,  or 
caused  outside  by  a  rib  of  metal  not  passing  evenly  through  the  die. 
They  are  due  many  times  to  hard  or  weak  spots  in  the  metal. 

(6)  Checks  are  very  small  tears. 

(7)  Rings  are  transverse  corrugations  in  the  tube  wall.    They  are 
caused  by  the  jumping  of  the  tube  in  drawing,  due  to  poor  bench 
equipment. 

(8)  Sinks  are  depressions  extending  around  the  inside  of  the 
tube.     They  are  caused  by  a  displaced  mandrel,  which  allows  the 
tube  to  draw  to  a  smaller  diameter  than  intended. 


FIG.  75. — Making  Hot-Drawn  Tubes.     Press  for  Cupping  Discs. 

(9)  Scratches  are  due  to  rough  dies  and  mandrels,  to  grit  picked 
up  by  the  tube  after  lubricating  for  drawing,  or  by  insufficient 
lubricating. 

203.  Hot-Drawn  Seamless  Tubes. — For  producing  seamless  tubes 
larger  than  6  inches  outside  diameter,  a  hot  drawing  process  is 
used.  In  this  process  a  plate  of  the  required  thickness  is  punched 
or  sheared  into  a  circular  disc.  This  disc  is  then  heated  to  a  bright 
red  heat  and  placed  in  a  hydraulic  press  arranged  as  in-  Fig.  75. 
The  disc  P  is  placed  over  the  circular  opening  in  the  die  block  D 
of  the  press,  and  the  plunger  H  is  forced  down  on  the  plate,  carry- 
ing it  completely  through  the  opening  in  the  die  block.  The  differ- 
ence in  the  diameters  of  the  openings  of  the  die  block  D  and  the 


THE  RE-MANUFACTUKE  OF  METALS 


183 


plunger  H  is  such  as  to  give  the  sides  of  the  cup  the  thickness  of  the 
disc.  The  squeeze  between  the  plunger  and  the  die  block,,  as  the 
disc  passes  through,  presses  the  sides  of  the  cup  free  from  wrinkles. 
This  operation  is  repeated  with  or  without  reheating  until  a  cup  is 


FIG.  76. — Making  Hot-Drawn  Tubes.     Re-Drawing  Cupped  Discs. 

produced  of  considerable  length.  The  form  of  the  die  used  in  the 
succeeding  operation  is  shown  in  Fig.  76.  The  die  is  recessed  to 
receive  and  locate  the  cup  produced  by  the  previous  operation  and 
frequently  the  bottom  of  the  cup  is  cooled  by  water  to  keep  the 
plunger  from  punching  a  hole  through  it. 


PIG.  77. — Cupped  Discs. 

The  plate  after  receiving  one  or  more  cupping  operations  in 
vertical  presses,  is  in  a  cupped  form  as  shown  in  Fig.  77.  Each  cup 
is  reheated  and  transferred  for  further  reduction  to  a  horizontal 
press  usually  called  a  hot-drawing  bench,  the  essential  features  of 


184 


MECHANICAL  PROCESSES 


which  are  shown  in  Figs.  78  and  79.  The  bench  consists,  of  a 
heavy  frame  placed  horizontally  and  connected  to  a  hydraulic 
cylinder  C.  In  operating,  the  cup  K  is  placed  over  the  end  of  the 


FIG.  78. — Hot-Draw  Bench  for  Elongating  Cupped  Discs. 

plunger  rod,  which  is  arranged  to  travel  the  entire  length  of  the 
bench  frame. 

Dies  X,  Y  and  Z ,  with  openings  of  successively  smaller  diameters, 
are  placed  in  suitable  holders  in  the  bench  frame.     The  cup  K  is 


FIG.  79.— Hot-Draw  Bench. 


pushed  through  the  dies  successively  as  shown  in  the  figure,  re- 
ducing the  diameters  and  the  wall  thickness.  Several  drawings 
are  made  in  this  manner,  reheating  between  each  operation  until 
the  tube  is  reduced  to  its  final  diameter  and  wall  thickness.  The 


THE  RE-MANUFACTUKE  OF  METALS  185 

bottom  of  the  cup  is  cooled  with  water  from  a  hose  to  keep  the 
plunger  rod  from  punching  a  hole  through  it  while  the  cup  is  pass- 
ing through  the  dies. 

After  reducing  the  tube  to  its  final  diameter,  the  bottom  is  sawed 
off,  the  ragged  edges  of  the  open  end  are  trimmed  off,  and  the  tube 
is  then  inspected  and  tested  under  hydrostatic  pressure. 

To  show  the  change  of  form  possible  in  hot  drawing,  a  tube  22 
feet  long  9*4  inches  inside  and  10  inches  outside  diameter  is  made 
from  a  round  plate  54  inches  in  diameter  and  1%  inches  thick. 
This  requires  ten  passes  through  as  many  different-sized  dies. 

Hot-drawn  tubes  may  be  further  cold  drawn  to  produce  tubes  up 
to  ten  inches  in  diameter. 

204.  Steel  Cylinders  for  Storage  of  Gases. — From  the  hot-drawn 
steel  tubes  just  described  are  made  seamless-steel  cylinders  for 


r      n 

FIG.  80. — Reducing  the  Opening  in  a  Hot-Drawn  Tube 

storage  of  gases  under  pressure.  The  bottom  is  left  on  the  tube  and 
the  open  end,  after  having  had  the  defective  part  trimmed  off,  is 
heated  and  pressed  under  the  dies  B  and  C  to  a  shape  shown  in 
Fig.  80.  The  opening  is  suitable  for  attaching  a  controlling  valve 
to  the  cylinder. 

These  containers  are  made  as  large  as  18  inches  in  diameter  and 
12  feet  long. 

Another  method  of  closing  the  tube  end  is  to  hold  the  tube 
strongly  in  a  rapidly  revolving  machine  of  great  rigidity  and  bring 
the  pressure  of  a  steel  roller  against  the  side  of  the  tube  end.  This 
pressure  is  so  great  that  its  friction  heats  the  tube  and  closes  it  to 
the  amount  desired.  The  process  is  called  spinning  and  may  even 
be  used  to  close  and  weld  a  tube  end  of  mild  steel. 

205.  Cold  Pressing  of  Metals. — The  ductility  of  many  metals,  in- 
cluding many  of  the  alloys,  is  sufficient  to  allow  sheets  of  the  metals 


186  MECHANICAL  PROCESSES 

to  be  pressed  cold,  without  injury,  into  a  great  variety  of  forms. 
A  considerable  change  of  shape  from  the  flat  sheet  may  be  accom- 
plished by  a  succession  of  gradual  changes,  as  was  seen  in  forming 
large  tubes  in  the  operations  of  making  hot-drawn  tubes.  The 
amount  of  distortion  which  can  be  accomplished  at  each  step  de- 
pends upon  the  power  applied,  and  upon  the  ductility  of  the  metal. 
The  metal  must  be  annealed  after  a  certain  degree  of  change  of 
shape,  else  its  ductility  is  lost  and  further  pressure  would  disrupt 
the  piece. 

Common  examples  of  the  application  of  this  process  are  cartridge 
cases,  small  round  tin  boxes,  embossed  metal  ceilings,  man-hole 
covers  for  boilers,  metal  ends  of  lead  pencils,  spoons,  and  many 
domestic  utensils. 

Many  articles  are  pressed  completely  at  one  operation,  and  many 
others  of  more  complicated  shape  are  pressed  in  two  or  more  suc- 
cessive operations  under  different  dies,  with  or  without  annealing, 
according  to  the  ductility  of  the  metal  used.  This  process  is  now 
applied  to  the  shaping  of  articles  from  cold  plates  of  mild  steel  as 
great  as  %  of  an  inch  thick,  although  the  thickness  of  steel  which 
can  be  shaped  cold  is  limited  only  by  the  power  of  the  shaping  press 
and  the  ductility  of  the  steel. 

The  machines  which  shape  thin  sheets  do  their  work  by  power 
transmitted  through  geared  wheels,  levers,  cams,  etc.,  to  properly 
placed  punches,  dies  and  plungers,  and  the  proper  lubrication  of 
the  work  is  essential.  These  machines  are  built  to  turn  out  work 
with  a  minimum  of  attendance,  and  many  of  them  carry  a  piece  of 
metal  through  the  several  steps  and  turn  out  the  finished  product 
automatically  so  long  as  sheet  metal  is  fed  to  them. 

The  shaping  of  heavier  sheets,  particularly  those  of  steel,  usually 
requires  hydraulic  presses,  although  very  powerful  machines  are 
built  for  heavy  work  similar  in  design  to  those  for  lighter  work. 

As  with  all  metal-shaping  processes,  particularly  do  these  proc- 
esses require  means  of  holding  the  metal  to  be  shaped  firmly  in  the 
position  or  positions  required. 

206.  Steps  in  Shaping  Articles  from  Sheet  Metals. — Fig.  81  shows 
the  steps  in  the  process  of  shaping  a  vessel  from  tin,  brass,  copper  or. 
other  sheet  metal.  The  first  step  is  to  stamp  out  the  disc,  No.  1, 


THE  RE-MANUFACTURE  OF  METALS 


18? 


from  the  flat  sheet,  called  cutting  or  blanking.  The  shapes  2,  3  and 
4  are  then  successively  stamped  between  upper  and  lower  dies 
which  are  counterparts  of  these  shapes.  This  kind  of  shaping  is 


FIG.  81. — Steps  in  Shaping  Sheet  Metal  by  Drawing  and  Spinning. 

known  as  drawing.  Shape  5  is  produced  by  spinning,  and  is  done 
on  a  type  of  lathe  shown  in  Fig.  82.  A  solid  shaping  roll  of  the 
contour  of  the  work  is  held  inside  the  shape  as  it  revolves,  and  the 


FIG.  82. — Spinning  Lathe. 


188 


MECHANICAL  PROCESSES 


FIG.  83.— Steps  in  Pressing  a  Vehicle  Hub  from  Steel  Plate. 


THE  KE-MANUFACTUKE  OF  METALS  189 

spinning  is  done  from  the  outside  by  pressure  of  a  burnishing  roll 
mounted  on  the  lathe  carriage. 

Any  embossing  or  lettering  raised  from  the  surface  of  the  metal 
is  done  by  stamping. 

Cylindrical  metal  boxes  several  inches  long  and  less  than  half  an 
inch  in  diameter,  can  readily  be  formed  from  discs  of  sheet  metal 
by  this  process. 

Another  example  of  cold  pressing  is  shown  in  Fig.  83.  This 
shows  the  gradual  changes  of  form  in  shaping  a  vehicle  hub  from  a 
steel  disc  %  inch  thick  and  15  inches  in  diameter.  The  flange  of  the 
finished  hub  is  7%  inches  in  diameter.  The  steps  are  numbered 
consecutively.  Annealing  is  necessary  after  about  each  third  step, 
judged  by  the  workmen  for  each  piece. 

207.  Drop  Forcings. — The  process  of  forging  small  articles  of 
iron  on  the  blacksmith's  anvil  is  well  known.  Hand  work  of  this 
kind  is  very  expensive  for  making  intricate  shapes  and  is  a  slow 
process  even  for  making  simple  shapes.  Various  processes  have 
been  employed  to  shape  iron  articles  in  quantity  which  will  be  at 
least  as  good  in  quality  and  less  expensive  than  forgings  made  by 
hand.  One  of  the  processes  so  employed  is  drop  forging.  By  this 
means,  a  great  variety  of  forgings  of  plain  and  intricate  shapes  can 
be  produced  in  large  quantities  far  cheaper  and  possibly  better  than 
by  means  of  hand  forging.  Drop  forgings  must  be  needed  in  large 
quantities  to  warrant  making  a  pair  of  dies,  as  these  are  expensive. 

A  drop  forging  is  made  by  the  drop  of  a  heavy  hammer  on  a 
piece  of  hot  iron  held  by  a  workman  on  the  anvil  of  the  machine. 
The  hammer  carries  a  die  which  shapes  the  upper  half  of  the 
forging,  and  the  anvil  holds  another  die  which  shapes  the  lower 
half. 


13 


190 


MECHANICAL  PROCESSES 


FIG.  84. — Drop  Hammer. 


THE  KE-MANUFACTURE  or  METALS  191 

208.  The  Drop  Hammer. — Fig.  84  shows  a  type  of  drop  hammer 
such  as  is  used  for  making  drop  forgings.     The  lower  die  is  held 
on  the  anvil  A  and  the  upper  die  is  held  under  the  hammer  B,  by 
keys  in  the  dovetails  shown.    The  dies  are  not  shown  in  this  view. 
The  uprights  of  the  machine  form  guides  between  which  the  ham- 
mer is  raised  and  dropped.     The  hammer  is  raised  by  a  smooth 
board  which  passes  between  two  cylindrical  rollers  at  the  top  or 
"  head  "  of  the  machine.     One  of  these  rollers  is  marked  (7.    Each 
roller  is  driven  by  its  own  shaft  and  belt  wheel.    The  two  belt  wheels 
are  marked  WW.    The  bearings  of  the  roller  shafts  are  arranged  so 
that  the  rollers  may  be  made  to  grip  the  board  or  may  be  separated 
to  allow  the  board  to  drop  between  them.    This  adjustment  of  the 
rollers  is  controlled  by  the  rod  D,  connected  to  the  foot  lever  G. 
The  workman  may  instantly  release  the  pressure  of  the  rollers  on 
the  board  and  cause  the  hammer  to  drop,  without  checking  the 
speed  of  the  rollers  themselves.    A  lever  H,  shown  in  front  of  the 
machine,  is  arranged  to  trip  the  hammer  automatically  so  that  it 
may  not  go  too  high. 

The  hammer  weighs  1000  Ibs.  or  more,  and  it  takes  but  a  few 
strokes  to  forge  a  considerable  mass  of  iron  into  shape. 

209.  Drop-Forging  Dies.    Making  a  Drop  Forging. — Dies  for  drop 
forgings  are  made  of  hardened  forged  steel,  of  cast  steel  or,  for 
roughing  out  large  work,  they  are  made  of  chilled  cast  iron.    Dies 
are  made  in  pairs,  as  shown  in  Fig.  85.    The  lower  contains  an  im- 
pression of  the  lower  part  of  the  forging,  and  the  upper  contains 
an  impression  of  the  upper  part.    For  some  forgings  the  face  of  the 
die  contains  a  rough  and  a  smooth  impression  of  the  forging. 

The  dies  in  Fig.  85  are  used  as  follows :  A  bar  of  iron  of  con- 
venient length  for  handling  and  of  sufficient  cross  section  to  fill  the 
dies  is  heated  in  a  small  oil  or  gas  furnace  nearby.  The  first  opera- 
tion is  to  place  the  end  of  the  heated  bar  along  the  lower  die  over 
the  impression  B  and  give  it  one  or  more  blows  with  the  hammer 
to  shape  it  roughly  to  the  outline  of  the  forging  to  be  made.  This 
is  called  breaking  down,  and  the  impression  at  the  opposite  edge 
of  the  dies  is  also  used  to  assist  in  this  work.  This  operation  is 
immediately  followed  by  placing  the  broken-down  end  over  the  die 
D  and  dropping  the  hammer  on  it,  usually  about  twice.  The  metal 
is  forced  into  both  dies,  completely  filling  them,  and  the  surplus 
metal  is  forced  into  the  slight  depression  surrounding  the  dies.  But 


192 


MECHANICAL  PROCESSES 


for  this  depression,  the  dies  could  not  come  together  and  the  forging 
would  be  too  thick.  The  fin  or  "  flash "  of  metal  thus  formed 
around  the  forging  is  shown  on  the  wrenches  marked  F.  The  flash 
is  cut  off  in  another  machine  called  the  trimming  press  which 
stands  alongside  the  drop  hammer.  The  finished  wrenches  are 
shown  at  G. 


FIG.  85. — Drop-Forging  Dies  and  Specimens  of  Work. 

To  keep  from  cutting  off  the  end  of  the  bar  in  process  of  being 
forged,  and  leaving  the  forging  with  no  holding  piece,  a  notch  is 
cut  in  one  end  of  each  die  as  shown  at  the  ends  of  the  wrench  dies. 
A  cutter  at  the  side  of  the  die  usually  cuts  off  a  forging  when 
shaped  as  shown  at  F.  Frequently  forgings  are  pickled  to  remove 
the  forge  scale  before  trimming  off  the  flash.  Large  forgings  and 
high-grade  small  forgings  are  annealed. 

Fig.  86  shows  a  pair  of  dies  B,  B,  for  an  automobile  engine 
crank-shaft,  and  C,  C,  show  the  two  parts  of  the  trimming  dies. 

Fig.  87  shows  the  steps  of  shaping  the  crank  shaft  from  the  bar  a. 
A  few  blows  of  the  hammer  break  it  down  at  the  side  of  the  die  to 
the  shape  b,  and  then  the  die  shapes  it  in  about  a  dozen  strokes  as  at  c. 


THE  EE-MANUFACTURE  OF  METALS 


193 


Fiu.  86. — Dies  for  Forging  and  Trimming  a  Small  Crank  Shaft. 


FIG.  87. — Steps  in  Forging  an  Automobile  Crank  Shaft. 


194 


MECHANICAL  PROCESSES 


The  trimming  press,  in  which  are  mounted  the  dies  C,  C,  cuts  off  the 
flash  as  at  d,  and  the  bull-dozer  or  upsetting  press  presses  a  flange 
on  the  end  e  after  a  reheating. 


FIG.  88, — Specimens  of  Drop  Forgings. 

After  annealing,  the  forging  is  ready  for  machining  to  its  re- 
quired dimensions. 

Fig.  88  shows  a  number  of  specimens  of  drop  forgings,  and  Fig. 


THE  RE-MANUFACTURE  OF  METALS 


195 


89  shows  a  high-grade  alloy  crucible-steel  forging  twisted  and  bent 
cold  to  show  its  quality. 

Long  forgings  are  forged  one  end  at  a  time  to  avoid  making  an 
unduly  long  die  and  having  to  handle  an  unwieldly  piece  of  work. 
An  automobile  axle  is  about  the  longest  drop  forging  made. 


PIG.  89. — A  High-Grade  Drop  Forging  Bent  and  Twisted  Cold. 

210.  Bolts,  Nuts  and  Rivets. — Bolts,  rivets  and  nails  are  pressed 
into  shape,  and  nuts  are  punched,  by  machines  specially  built  for 
this  work. 

Fig.  90  shows  the  general  arrangement  of  a  machine  for  pressing 
bolts,  rivets  and  wire  nails.  The  end  of  a  coil  of  wire  or  rod  R  is 
fed  by  two  or  more  pairs  of  grooved  roller  wheels  through  a  guide 


FIG.  90. — Rivet-Pressing  Machine. 

(r.  When  the  end  is  far  enough  through,  the  feeding  wheels  stop 
and  the  two  clamps  CC  close  together  and  grip  the  material  firmly. 
The  die  D  then  moves  forward  through  its  guide,  in  the  direction 
of  the  arrow,  presses  the  head  H  into  shape,  and  then  moves  back. 
The  clamps  CC,  release  their  hold,  move  back,  a  cutter  moves 
along  the  face  F8  of  the  guide  G  and  shears  the  rivet  from  the  rod 
at  S,  and  it  falls  into  the  box  under  the  machine.  When  the  cutter 


196  MECHANICAL  PROCESSES 

has  moved  out  of  the  way,  the  feeding  wheels  again  revolve,  the 
material  is  fed  in,  and  the  operation  is  repeated. 

The  die  D  may  be  replaced  by  others  to  give  different  shaped 
heads  (for  nails  or  bolts). 

The  clamps  C  may  take  part  in  the  shaping,  as  in  pressing  barbs 
on  the  body  of  a  nail,  in  addition  to  performing  their  work  of 
gripping  and  holding. 

Eivets  and  rough  bolts  up  to  %-inch  diameter  may  be  pressed 
cold  from  soft-steel  material.  If  hot  material  is  fed  into  the 
machine,  it  is  in  the  form  of  straight  bars  and  not  in  coils.  Only 
a  few  feet  of  the  bar  is  heated  and  when  this  is  used  up  by  the 
machine,  the  remaining  end  is  then  heated. 

Boiler  rivets  and  the  better  grades  of  bolts  are  hot  pressed. 
Sometimes  they  are  cut  to  length  before  heating  for  pressing,  and 
the  head  may  be  pressed  in  two  heats.  This  is  done  in  high-grade 
work.  Boiler  rivets  are  always  annealed  after  they  are  formed. 

Bolts  are  often  cut  from  rods  of  solid  metal  in  bolt-cutting 
machines. 

Square  and  hexagonal  nuts  are  pressed,  punched,  and  sheared 
from  long,  flat  bars.  Nuts  are  also  cut  by  machines  from  bars  of 
square  or  hexagonal  cross  sections. 

211.  Screw-Cutting  Machines. — These  are  machines  of  ingenious 
design  which  make  a  great  variety  of  small  metal  objects  from 
round,  square,  hexagon  or  other  shaped  rods  of  brass,  bronze  and 
steel.  They  embody  a  very  high  degree  of  mechanical  ingenuity, 
and  the  rapidity  and  accuracy  with  which  they  turn  out  a  superior 
grade  of  work  is  remarkable.  Xot  only  do  they  make  all  kinds  of 
machine  and  other  screws,  particularly  in  medium  and  small  sizes, 
but  they  make  an  endless  variety  of  small  articles  too  thick  or 
intricate  to  be  made  by  the  drawing  and  spinning  processes  men- 
tioned for  shaping  sheet  metals. 

Fig.  91  shows  an  automatic  screw  machine.  It  is  so  equipped 
and  geared  that  when  a  rod  of  metal,  usually  about  16  feet  long, 
is  placed  through  the  main  spindle  at  ~B,  and  the  machine  started, 
it  continues  work  unattended  until  the  rod  is  entirely  cut  into 
articles  which  the  machine  is  at  the  time  set  to  produce. 

The  rod  is  gripped  by  a  small  chuck  C,  with  enough  of  the  rod 
end  extending  beyond  the  chuck  to  be  operated  upon  by  the  various 


THE  RE-MANUFACTURE  OF  METALS 


197 


cutters.  Most  of  the  cutters  are  mounted  on  a  small  turret  T,  the 
axis  of  which  is  horizontal  and  at  right  angles  to  the  axis  of  the 
spindle.  The  shaft  which  carries  the  turret  is  mounted  on  a 
.carriage  D  which  can  slide  back  and  forth  parallel  to  the  direction 
of  the  spindle  axis.  The  whole  mechanism  is  so  geared  together 
that  the  part  of  the  rod  extending  beyond  the  chuck  is  operated  on 
successively  by  each  of  the  six  tools  clamped  on  the  turret  and  re- 


FIG.  91. — Automatic  Screw-Cutting  Machine. 

volved  into  place  at  the  proper  time.  In  this  way  the  accumulated 
cutting  of  the  several  tools  on  the  rod  end,  each  tool  doing  its  par- 
ticular part  of  the  cutting,  shapes  the  pieces  as  required.  When  so 
shaped,  a  cutter  cuts  the  piece  off  the  rod  end,  and  it  falls  into  a 
box  below.  The  rod  is  then  automatically  fed  in  a  definite  amount 
for  the  cutting  operations  to  be  repeated. 

The  machine  has  an  attachment,  not  here  shown,  for  cutting  a 
screw  driver  slot  in  the  head  of  a  screw  after  it  is  cut  from  the  rod. 


198 


MECHANICAL  PROCESSES 


212.  Examples  of  Work  from  the  Screw  Machine. — Fig.  92 
shows  a  variety  of  small  articles  made  on  screw  machines.  The 
sizes  of  these  articles  vary  in  length  from  a  fraction  of  an  inch  to 


vv- 


FIG.  92. — Products  of  the  Automatic  Screw  Machine. 

more  than  two  inches.  The  specimens  shown  are  pointed  to  the 
right  the  same  as  they  were  held  in  the  machine  during  the  process 
of  making.* 


*  Paragraph  439  of  the  Appendix  outlines  the  work  of  cutting  the 
piece  W  of  Fig.  92. 


CHAPTER  VII. 

SHOPS  OF  MACHINERY  BUILDING  AND  REPAIRING  PLANTS. 
DRAWINGS  FOR  SHOP  USE. 

213.  Distinctive  Features  of  Building  and  Repairing  Plants. — 

The  building  of  ships,,  engines,  locomotives,  machine  tools  and 
large  machines  for  a  great  diversity  of  purposes  necessitates  bring- 
ing together  the  products  of  several  different  shops.  While  each  of 
these  shops  considered  alone  is  virtually  a  place  for  the  re-manu- 
facture of  metals  along  its  own  particular  lines,  the  assembled 
products  of  the  several  shops  present  such  a  diversity  of  construc- 
tion and  each  machine  or  structure  so  built  has  so  distinctive  an 
identity  of  its  own,  that  an  establishment  made  up  of  an  assemblage 
of  such  shops  is  regarded  as  beyond  the  limitations  of  a  re-manu- 
facturing plant. 

For  example,  •  a  ship  or  a  locomotive  is  a  much  more  distinctive 
product  than  the  plates,  castings,  bolts,  rivets,  pipes,  etc.,  which 
compose  it,  and  the  assemblage  in  one  establishment  of  the  different 
metal-working  shops  required  to  build  either  embodies  the  capacity 
for  turning  out,  quite  as  readily,  machines  or  structures  of  many 
other  kinds. 

Assemblages  of  shops  capable  of  uniting  such  a  diversity  of  roll- 
ing mill  and  re-manufactured  products  into  highly  complex  con- 
structions are  also  most  advantageously  fitted  as  general  repair 
shops,  and  particularly,  because  of  its  accessibility,  is  a  shipbuild- 
ing plant  also  an  extensive  ship-repairing  plant. 

214.  Shops  Composing  a  Building  and  Repairing  Plant. — The  im- 
portant shops  of  a  large  building  and  repairing  plant  are : 

(1)  The  Woodworking   shop,   including   the   Pattern   and   the 
Joiner  shops,  sometimes  separate. 

(2)  The  Foundry. 


200  MECHANICAL  PROCESSES 

(3)  The  Blacksmith  or  Forge  shop. 

(4)  The  Machine  shop. 

(5)  The  Boiler  shop. 

(6)  The  Copper  and  Sheet  Metal  shop,  sometimes  divided  into 
two  shops. 

(7)  The  Plate  and  Angle  shop,  for  shipyards  and,  to  a  less  ex- 
tent, for  bridge  material  plants. 

Of  prime  importance  to  any  manufacturing  plant  is  the  drafting 
room,  or  drawing  room,  in  which  the  design  of  machinery  parts  is 
worked  out  and  drawings  of  these  parts  are  made  to  guide  the 
several  shops  in  shaping  their  respective  parts  for  the  complete 
machine.  In  a  ship-building  plant  the  drawings  of  the  ship's  hull 
are  elaborated  by  scribing  them  out  to  full  size  on  the  floor  of  the 
mould  loft  as  the  best  means  of  obtaining  the  exact  form  of  the 
various  individual  frames  and  plates  of  which  the  hull  is  composed. 

A  very  essential  adjunct  to  the  machine  shop  is  the  erecting 
shop,  where  the  finished  parts  of  a  machine  are  assembled  and 
secured  together  as  a  complete  unit.  All  engines  and  large 
machines  are  thus  assembled  and  tried,  after  which  they  are  dis- 
mantled and  moved  away. 

Of  indispensable  importance  in  metal  producing  and  many  metal 
shaping  establishments  are  (a)  the  chemical  laboratory  for  analyz- 
ing materials,  (b)  the  testing  room,  for  testing  the  strength  of 
materials,  and  (c)  the  inspecting  department  for  inspecting  and 
testing  finished  products. 

215.  The  Drawing  Room. — When  a  designer  has,  determined 
upon  the  action,  position,  form  and  material  of  each  part  of  a 
machine,  his  ideas  are  sent  to  the  drawing  room  in  one  or  more 
sketches.  From  these  an  assembled  drawing  is  made  of  the  whole 
machine,  to  a  definite  scale,  and  by  aid  of  the  sketches  and  the 
assembled  drawing,  detail  drawings  are  made  in  larger  scale,  con- 
venient for  showing  the  details  of  each  part  and  for  recording  the 
dimensions. 

In  the  design  of  a  ship,  bridge,  structure  or  machine  of  any  kind, 
the  kind  and  quality  of  materials  to  be  used  must  be  determined  by 


SHOPS  OF  MACHINERY  BUILDING  PLANTS  201 

the  designer.,  who  must  also  determine  the  size  and  shape  of  each 
part  with  a  view  to  giving  it  the  required  strength. 

216.  Drawing-Room  Methods. — Assembled  and  detail  drawings 
are  first  made  in  pencil  on  a  quality  of  heavy  white  or  straw-colored 
paper  which  will  stand  considerable  erasing.     A  sheet  of  tracing 
cloth  is   placed  over  this  work,  when  completed,   and   the   work 
copied,,  or  traced,  in  ink.     The  tracing  is  then  used  for  making 
blue  prints  or  black  prints  and  is  kept  on  file  in  the  drawing  room. 
Many   drawing  rooms  are  provided  with  a  fire  and  water-proof 
vault  for  the  safe  keeping  of  valuable  tracings. 

217.  Shop  Drawings. — The  shops  must  be  supplied  with  draw- 
ings of  any  piece  of  machinery  to  be  made,,  as  guides  to  the  work- 
men.    These  drawings  are  usually  blue  or  black  prints  made  from 
the  tracings,  as  mentioned  in  the  preceding  paragraph. 

The  information  in  the  following  items  should  be  shown  by  a 
drawing : 

(1)  One  or  more  views  of  the  article,  amplified  by  cross-section 
views  where  needed,  to  show  fully  its  form. 

(2)  Dimensions  sufficient  to  make  the  article  to  the  exact  size 
required,  and  sufficient  to  save  the  workman  the  necessity  of  adding 
several  dimensions  to  find  another  dimension. 

(3)  Designation  of  the  material  or  materials  of  which  the  piece 
is  to  be  made. 

(4)  Designation  of  the  number  of  pieces  required. 

(5)  Indications  of  any  special  features  of  material,  finish,  or 
changes  from  usual  conditions. 

(6)  The  scale  to  which  the  drawing  is  made,  or  the  designation 
of  the  scale  of  each  of  the  parts  if  they  are  drawn  to  different  scales 
on  the  same  drawing. 

(7)  The  title  and  number  of  the  drawing,  giving  names  and  uses 
of  the  parts  shown,  date  of  authorization  and  name  of  authority 
approving  the  drawing,   and,   if  the  drawing  supersedes  another 
drawing,  a  statement  to  this  effect,  giving  name,  date  and  number 
of  superseded  drawing. 


202  MECHANICAL  PROCESSES 

218.  Methods  of  Representing  Articles  on  Drawings. — Figures 
93  and  94  are  examples  of  two  methods  of  showing  an  article  on  a 
drawing.     The  former  is  the  orthographic  method  which  shows 
three  views  projected  upon  three  planes  of  reference  as  used  in 
descriptive  geometry,  and  the  latter  is  the  isometric  method,  used 
particularly    in    free-hand    sketches    and    now    used    on    finished 
drawings. 

In  many  cases,  two  orthographic  views  will  show  fully  the  details 
of  an  article,  particularly  if  one  is  a  cross-section  view.  Simple 
articles  may  be  shown  by  one  view.  In  Fig.  94  the  isometric  axes 
AB,  AC  and  AD  are  120°  apart,  that  is,  the  angles  CAD,  DAB  and 
CAB  are  120°,  with  AB  vertical. 

219.  Consecutive  Order  of  Shop  Work. — It  is  a  part  of  the  work 
of  the  designer  of  any  mechanical  structure  or  machine  to  determine 
not  only  the  material  of  which  each  piece  of  the  structure  is  to  be 
made,  but  the  general  method  of  making  it,  which  necessarily  in- 
cludes a  designation  of  the  shops  in  which  the  work  is  to  be  done. 

If  an  article  is  to  be  shaped  in  cast  iron,  cast  steel,  or  other  cast 
metal,  a  pattern,  usually  of  wood,  must  first  be  made  in  the  pattern 
shop.  This  is  made  according  to  dimensions  and  other  information 
given  on  the  drawing.  This  pattern  is  used  in  the  foundry  as  a 
model  for  a  mould,  which,  when  prepared,  is  poured  with  molten 
metal.  The  piece  thus  cast  more  or  less  roughly,  is  cleaned  and 
used  sometimes  without  further  work  upon  it,  but  if  accurate 
fitting  and  exact  dimensions  are  necessary  for  the  casting,  it  goes 
to  the  machine  shop  to  be  machined,  and  possibly  ground  if  very 
accurate  fitting  is  needed. 

If  the  article  is  to  be  made  as  a  forging,  a  bloom,  billet,  or 
smaller  piece  from  the  rolling-mill  stock  kept  on  hand  is  forged 
to  the  required  shape  either  by  hand  or  by  steam  hammer  in  the 
blacksmith  shop,  and  the  forging  may,  in  some  cases,  be  used  just 
as  it  comes  from  the  anvil,  or,  if  it  must  be  finished  to  particular 
shape  and  dimensions,  it  goes  to  the  machine  shop. 

Many  articles  may  be  made  in  the  machine  shop  directly  from 
rods,  bars,  plates  and  shapes  from  the  rolling  mill,  without  having 
been  given  preliminary  form  in  the  foundry  or  the  blacksmith  shop. 


SHOPS  or  MACHINERY  BUILDING  PLANTS 


203 


FIG.  93. — Orthographic  Projections. 


FIG.  94. — Isometric  Projection. 


204  MECHANICAL  PROCESSES 

The  boiler  shop  works  into  shape  plates,  sheets,  tubes,  ete.j,  direct 
from  the  rolling  mill,  and  fittings  produced  in  other  shops. 

The  copper  and  sheet-metal  shop  draws  its  sheet  material  direct 
from  the  rolling  mill.  Much  copper  and  brass  tubing,  obtained 
from  the  tube  mills,  is  used  in  the  copper  shop. 

The  plate  and  angle  shop  uses  plates  and  structural  shapes  sup- 
plied direct  from  the  rolling  mills. 

All  shops  of  building  and  repairing  plants  find  more  or  less  use 
for  bolts,  rivets,  screws,  and  various  other  products  of  the  re- 
manufacturing  industries  in  connection  with  their  own  shop 
products. 


CHAPTER  VIII. 
THE  PATTERN  SHOP. 

220.  Work  of  the  Pattern  Shop. — This  shop  is  a  woodworking 
shop  devoted  to  the  making  of  wood  patterns  for  the  foundry. 
These  patterns  are  used  as  models  for  shaping  moulds  of  articles  to 
be  cast  from  molten  metals. 

A  pattern  maker  must  be  an  expert  woodworker,  and  must  be 
skilled  in  reading  correctly  the  most  intricate  mechanical  drawings. 
He  must  also  be  versed  in  the  methods  used  by  the  foundryman  in 
making  moulds,  to  know  how  to  make  patterns  in  forms  best  suited 
to  foundry  requirements  yet  not  unnecessarily  costly. 

Cabinet  making  and  joiner  work  may  be  done  by  pattern  makers 
with  pattern-shop  equipment,  but  in  large  ship  and  machine-build- 
ing establishments,  the  pattern  shop  and  joiner  shop  are  usually 
separate. 

221.  Pattern-Shop    Equipment. — The    woodworking    appliances 
which  compose  the  pattern-shop  equipment  may  be  divided  into 
(1)  power  tools  (machine  tools  driven  by  power),  (2)  hand  tools, 
and   (3)   accessory  appliances  such  as  work  benches,  clamps,  glue 
pots,  etc. 

222.  Power  Tools. — Machines  of  this  kind  are,  in  all  kinds  of 
shops,  labor-saving  devices.     While  many  such  machines  might  be 
omitted  from  a  shop  equipment,  the  time  and  cost  for  turning  out 
work  without  them  would  be  greater  than  if  the  machine  were  used, 
and  in  many  cases  hand  work  would  be  less  accurate. 

The  usual  power-tool  equipment  of  pattern  shop  includes : 

(1)  Circular  saw.  t    v 

(2)  Wood  lathes,  usually  large  and  small  sizes. 

(3)  Face  lathe. 

(4)  Band  saw. 

(5)  Hand  planer,  or  jointer. 

(6)  Surface  planer. 

(7)  Boring  machine. 

(8)  Mortise  machine. 

(9)  Scroll  saw. 
14 


206 


MECHANICAL  PROCESSES 


(10)  Emery  wheel. 

(11)  Grind  stone. 

The  variety  and  quantity  of  work  to  be  done  in  a  shop  determine 
its  power-tool  equipment,  hence  in  many  small  shops  some  of  the 
tools  of  the  foregoing  list  may  be  omitted,  while  in  the  most  ex- 
tensively equipped  shops  some  special  tools  not  here  named  may  be 
installed. 

223.  The  Circular  Saw. — Fig.  95  shows  a  type  of  circular-sawing 
machine  such  as  is  used  for  pattern-shop  work.  This  machine  con- 


FIG.  95. — Circular  Saw. 

sists  essentially  of  (1)  a  frame  which  carries  the  saws,  saw  mech- 
anism and  table;  (2)  a  flat-topped  saw  table  of  ribbed  cast  iron, 
and  (3)  one  or  two  saws  mounted  ready  for  use. 

The  saw  table  is  made  in  two  sections,  divided  along  AB.  Both 
sections  always  remain  in  the  same  plane  relative  to  each  other, 
but  the  part  C  is  mounted  on  suitable  slides  on  which  it  may  be 
moved  back  and  forth  in  the  direction  AB  parallel  to  the  plane  of 
the  saw.  Small  work  to  be  sawed  is  held  by  hand  against  the  guide 
or  "  fence  "  D  which  may  be  set  so  that  the  end  of  the  piece  of 
work  will  be  cut  off  at  any  angle  desired  as  the  movable  table  carries 


THE  PATTERX  SHOP  207 

it  past  the  saw.  The  block  G  may  be  adjusted  along  the  stop  rod 
for  gaging  the  length  to  which  pieces  are  sawed. 

When  the  machine  is  used  for  ripping  boards  into  narrower 
widths,  the  ripping  fence  F  is  set  as  a  guide  at  the  distance  from 
the  saw  necessary  for  cutting  the  widths  required.  Eipping,  or 
sawing  along  the  grain  of  wood,  is  done  by  the  coarse-toothed  saw 
for  more  rapid  working. 

While  the  upper  saw  is  in  use,  the  belt  which  drives  the  saws  is 
not  in  contact  with  the  belt  wheel  of  the  lower  saw,  hence  this  saw 


H- 


PIG.  96. — Woodworking  Lathe. 

is  idle.  When  the  lower  saw  is  to  be  used,  it  is  revolved  into  posi- 
tion by  turning  the  wheel  W  while  the  machine  is  not  running,  and 
as  one  saw  is  carried  into  position  for  use,  the  other  is  simulta- 
neously carried  below  the  table. 

The  saw  table  may  be  tilted  about  AB  as  an  axis  for  sawing  at 
an  angle.  The  saws  should  run  at  about  600  revolutions  per 
minute. 

224.  The  Speed  Lathe. — This  is  the  common  designation  for  a 
small  wood-turning  lathe,  which  turns  at  high  speed.  As  the 
cutting  is  done  by  hand  tools,  this  lathe  is  sometimes  called  a  hand 
lathe.  Fig.  96  shows  a  view  of  this  lathe.  Its  main  parts  are :  A, 
Bed;  B,  Head  stock;  G,  Tail  stock;  D,  Tool-rest  holder. 


208 


MECHAXICAL  PROCESSES 


Work  is  held  in  the  lathe  between  the  live  center  F  and  the  dead 
center  Gt  or  the  live  center  is  punched  out  by  means  of  the  rod  II 
and  the  work  is  fastened  by  screws  to  the  face  K,  shown  in  Fig.  97. 
As  the  work  revolves  it  is  shaped  by  hand  tools  steadied  on  the  tool 


FIG.  97.— Lathe  Headstock. 

rest  M.     The  live  center  drives  the  work  when  it  is  suspended 
between  centers. 

The  head  stock  carries  a  hollow  steel  spindle  which  is  made  to 
revolve  at  different  speeds  by  a  belt  on  one  of  the  cone  pulleys  E. 
Fig.  97  shows  a  cross  section  of  the  moving  parts  of  the  head  stock. 


FIG.  98. — Specimens  of  Wood-Lathe  Work. 

Fig.  98  shows  two  examples  of  work  turned  in  this  lathe.  The 
piece  C  is  held  between  centers  and  the  piece  F  is  held  only  on  the 
face  plate. 

The  tail  stock  may  be  moved  along  the  lathe  bed  to  suit  the 
length  of  work,  and  when  it  is  clamped  to  the  bed,  the  dead  center 
may  be  moved  back  and  forth  by  turning  the  wheel  L. 


THE  PATTERN  SHOP  209 

These  lathes  are  used  not  only  for  turning  wood,  but  are  adopted 
to  finishing  articles  of  metal  after  they  have  been  roughed  to  shape 
in  a  machine  lathe.  For  hand  turning  of  metals,  different  tools 
are  used  from  those  for  turning  wood. 

The  swing  of  a  lathe  is  the  diameter  of  work  which  can  revolve 
freely  between  the  centers  and  the  lathe  bed  or  its  attachments. 
The  distance  between  centers  is  the  length  of  work  which  may  be 
held  between  the  lathe  centers.  These  definitions  apply  to  all 
classes  of  lathes,  in  either  pattern  or  machine  shop,  and  are  the 
measurements  by  which  the  sizes  of  lathes  are  designated. 


'•••"• 
FIG.  99. — Turning  Tools  for  Wood  Lathes. 

225.  Turning  Tools. — Fig.  99  shows  the  turning  tools  ordinarily 
used  with  wood  lathes.    Xaming  from  left  to  right  they  are: 

(1)  Round-nose  chisel.  (5)  Skew  chisel. 

(2)  Flat  scraping  chisel  (6)  Double-end  skew  chisel. 

(3)  Gouge.  (7)  Combination  roughing  and 

(4)  Diamond-point  chisel.  smoothing  chisel. 

lumbers  C  and  7  are  used  only  on  larger  size  lathes,  and  are 
clamped  in  a  tool  holder.  Fig.  100  shows  a  tool  holder  which 
may  be  used  on  small  or  large  lathes.  It  is  at  present  rigged  for 
holding  hand  tools. 

226.  The  Wood  Lathe. — This  designation  is  given  to  the  pattern- 
shop  lathe  for  turning  large  work. 

It  embodies  the  same  features  as  the  small  lathe,  and  is  operated 
in  the  same  way.    Hand  tools  may  be  used  for  cutting,  or  a  heavier 


210 


MECHANICAL  PROCESSES 


tool  may  be  clamped  in  the  tool  post  which  holds  the  bar  of  the 
hand-tool  holder  shown  in  Fig.  100. 

Most  large  lathes  are  equipped  with  a  movable  tool  carriage  in 
place  of  the  tool-rest  holder,  which  moves  by  hand  or  by  power 


FIG.  100.— Tool  Holder. 


feed  along  the  lathe  bed.     The  view  in  Fig.  100  shows  the  upper 
part  of  a  carriage  of  a  large  lathe. 

227.  The   Face  Lathe. — This   lathe  consists  merely  of   a  head 
stock  mounted  for  carrying  a  large  face  plate.    It  is  used  for  turn- 


FIG.  101. — Face  Lathe. 

ing  flat  work  of  large  diameter.     This  type  of  lathe  is  shown  in 
Fig.  101. 

228.  The  Band  Saw.— This  machine  is  shown  in  Fig.  102.    It  is 
used  for  sawing  along  straight  or  curved  lines,  and  may  be  used  for 


THE  PATTERN  SHOP 


211 


light  or  heavy  work,  according  to  the  size  of  the  saw  on  the 
machine.  Several  saws  are  provided.  They  are  endless  steel  bands 
with  teeth  along  one  edge. 


FIG.  102. — Band  Saw. 

Work  is  placed  on  the  table  T.  The  saw.,  which  is  carried  on  two 
large  rubber-tired  wheels,  moves  through  a  slit  in  the  table,  and  is 
driven  by  the  lower  wheel. 

For  most  work,  the  table  T  is  perpendicular  to  the  path  of  the 
saw,  but  the  table  may  be  tilted  about  the  slot  as  a  horizontal  axis, 
for  sawing  at  an  angle,  and  is  clamped  by  the  handle  P. 


212 


MECHANICAL  PROCESSES 


To  prevent  the  saw  being  pushed  gradually  off  the  wheels  by  the 
pressure  of  the  work  against  it,  the  back  edge  rubs  against  two 
guides,  the  upper  of  which  is  carried  by  a  stem  //  which  may  be  raised 
or  lowered  to  suit  various  thicknesses  of  work,  and  which  is  clamped 
in  position  by  the  handle  K.  The  saw  is  kept  taut  over  both  wheels, 
which  are  kept  in  the  same  plane  by  the  tilting  screw  M. 

It  is  well  to  note  that  the  more  recent  designs  of  all  classes  of 
machines  in  all  shops  are  provided  with  guards  and  protectors  to 


FIG.  103.— Hand  Planer. 

protect  workmen  from  injury.  The  saw  here  described  is  guarded 
by  casing  not  shown  in  the  figure.  Many  machines  are  provided 
with  means  for  stopping  them  automatically  in  case  of  accident. 

229.  The  Hand  Planer. — This  machine,  shown  in  Fig.  103,  is 
also  known  as  a  jointer.  It  is  used  to  cut  the  face  or  edge  of  a 
board  to  a  plane  surface,  to  chamfer  corners,  to  gain,  check,  plow, 
match,  etc.  Board  edges  and  parts  of  patterns  are  cut  true  in  this 
machine  to  enable  them  to  fit  closely  together  for  gluing.  This 
machine  does  the  work  of  a  man  with  a  hand  plane,  and  is  best 
adapted  to  small  work  which  may  be  easily  lifted  and  handled. 


THE  PATTERN  SHOP  213 

The  machine  consists  essentially  of  a  base,  on  which  is  mounted 
two  flat  tables  B  and  C,  one  slightly  higher  than  the  other,  a  cutter 
head  H,  and  a  "  fence  "  D  which  serves  as  a  guide  for  the  work. 

Either  table  may  be  raised  or  lowered  a  small  amount  to  regulate 
the  cut  of  the  knives  carried  by  the  cutter  head,  and  may  be 
moved  horizontally  to  or  from  the  cutter  head  to  give  ample  clear- 
ance for  the  knives  and  for  shavings.  The  work  to  be  planed  is 
pushed  along  on  the  table  by  hand  over  the  rapidly  revolving 
cutter  head,  the  two  knives  of  which  are  set  to  take  equal  depths  of 
cut  from  the  under  surface  of  the  wood.  The  cutter  head  consists 
of  a  steel  cylinder  slotted  for  holding  the  two  long  knives  which 
are  held  in  place  by  small  screws. 

Many  forms  of  grooves  may  be  cut  by  setting  in  one  of  the  knife 
slots  a  knife  with  its  edge  of  the  required  contour. 

230.  The  Surface  Planer. — This  machine  is  constructed  with  the 
same  method  of  cutting  provided  for  the  hand  planer,  but  it  is  a 
much  heavier  machine,  and  is  used  for  surfacing  rough  boards  and 
timbers.     Its  table  is  made  in  one  flat  piece  fitted  to  be  raised  or 
lowered  readily  to  suit  the  thickness  of  the  board  or  timber  passing 
under  the  knives.    The  work,  resting  on  the  table,  passes  under  the 
cutter  head,  also  it  passes  under  rollers  which  hold  it  down  before 
and  after  it  reaches  the  cutter  head.     These  rollers  feed  the  work 
along  the  table. 

231.  The   Boring  Machine. — This  machine  is  used  for  boring 
holes,  and  consists  essentially  of  a  round  spindle  held  horizontally 
or  vertically  in  suitable  bearings.     The  spindle  carries   a  bit  or 
auger  and  is  made  to  revolve  rapidly.     The  work  to  be  bored  is 
placed  on  a  suitable  stand  and  remains  stationary  while  the  spindle 
moves  in  the  direction  of  its  length  as  it  revolves,  until  the  bit 
cuts  into  the  material  to  the  desired  depth.    In  some  designs  of  this 
machine  the  spindle  merely  revolves  and  the  material  is  fed  against 
the  bit. 

232.  The  Mortise  Machine. — This  machine  is  used  to  cut  square 
or  rectangular  holes  in  wood.     It  consists  essentially  of  a  vertical 
shaft  which  is  made  to  oscillate  in  the  direction  of  its  length,  and 
which  carries  a  heavy  chisel  at  the  lower  end.    Mortising  machines 
are  often  worked  by  the  pressure  of  the  foot,  without  machine 
power. 


214  MECHANICAL  PROCESSES 

233.  Hand  Tools. — The  hand  tools  of  pattern  making  are  more  or 
less  familiar  as  those  used  in  carpentry  work.  Attention  will  be 
called  to  a  few  special  tools  and  features. 

Saw  Teeth. — In  sharpening  saw  teeth,,  the  file  should  be  held 
at  an  angle  to  the  plane  of  the  saw  blade  so  that  the  teeth  will 
present  an  appearance  shown  in  Fig.  104.  The  teeth  should  also 
be  "  set "  to  keep  the  wood  from  binding  the  sides  of  the  saw. 
This  is  done  by  bending  the  teeth  marked  c  slightly  to  one  side  of 


FIG.  104. 

the  plane  of  the  saw,  and  by  bending  those  marked  b  slightly  to 
the  other  side.  In  this  way  the  saw  cut  is  slightly  wider  than  the 
blade  thickness  of  the  saw. 

The  teeth  of  circular  saws  may  be  "  set "  or  may  be  "  swaged/' 
In  swaging,  the  teeth  are  not  bent  to  one  side,  but  the  tooth  end 
is  expanded  by  a  swage  and  hammer  so  that  its  cut  is  wider  than 
the  thickness  of  the  saw. 


Y 


FIG.  105. — Trammel  Points. 

Trammel  Points. — For  describing  arcs  of  large  radii,  a  pair  of 
trammel  points,  A  and  B,  are  mounted  on  a  bar  of  wood  or  metal 
as  shown  in  Fig.  105.  These  points  may  be  clamped  at  any  posi- 
tion along  the  bar. 

Wood  Trimmer. — A  very  useful  pattern-shop  tool  is  the  wood 
trimmer,  shown  in  Fig.  10G.  This  machine  is  much  used  to  cut 
ends  of  wood  pieces  to  an  exact  angle  "(usually  square)  with  the 
face  or  edge  of  the  piece.  It  consists  essentially  of  a  flat  table  B 
along  the  rear  edge  of  which  slides  a  triangular-shaped  piece,  carry- 


THE  PATTERN  SHOP 


215 


ing  two  knives  C  and  D.  The  plane  of  these  knives  is  exactly  90° 
to  the  plane  of  the  table.  The  guide  pieces  F  and  G  have  their 
faces  perpendicular  to  the  plane  of  the  table,  and  they  may  be 
swung  around  on  vertical  axes  and  clamped  at  any  desired  angle 
to  the  plane  of  the  knives.  A  piece  of  work  to  be  cut  is  held 
securely  by  the  hand  in  the  angle  formed  between  one  of  the  guides 
F  or  G  and  the  table,  and  the  knife  cuts  off  the  projecting  edge. 


FIG.  106. — Wood  Trimmer. 

The  large  wheel  at  the  back  of  the  trimmer  moves  the  knives  back 
and  forth  along  the  table  edge. 

234.  Materials  used  for  Patterns.— The  usual  and  best  adapted 
material  for  patterns  is  wood,  although  a  great  many  foundries 
which  make  large  quantities  of  one  article  use  patterns  made  of 
brass  or  other  metals,  to  avoid  excessive  wear  on  them. 

A  suitable  wood  for  patterns  must  have  the  following-named 
requisites : 

(1)   It  must  be  well  seasoned  and  must  not  warp. 


216  MECHANICAL  PROCESSES 

(2)  It  must  be  straight  grained  and  free  from  large  or  small 
knots  which  will  interfere  with  ready  working  or  prevent  a  smooth 
finish. 

(3)  It  must  not  be  subject  to  shrinkage  with  age. 

The  three  woods  much  used  for  patterns  are  white  pine,  mahog- 
any, and  cherry,  although  other  woods  are  more  or  less  used  in 
many  localities.  Red  wood  is  much  used  on  the  Pacific  coast. 
Mahogany  is  the  best  of  these  woods,  but  it  is  expensive  and  its  use 
is  therefore  limited  to  small  and  medium-sized  patterns  requiring 
durability  and  permanence  of  shape. 

Pine  is  much  used  for  large  patterns  and  for  the  ordinary  run  of 
small  patterns. 

235.  Joints  and  Cuts  in  Woodworking. 

Ripping  is  sawing  wood  along  the  grain. 

Cross  cutting  is  sawing  across  the  grain. 

A  warped  board  is  said  to  be  out  of  wind.  It  may  be  planed 
straight  in  the  planer  if  only  moderately  out  of  wind  so  that  but 
little  material  needs  to  be  removed. 

In  Fig.  107  the  cuts  commonly  designated  in  woodworking  arc 
lettered  as  follows : 

a.  a.  Chamfering  or  cornering. 

b.  Rabbeting. 

c.  Filleting  (in  contrast  to  square  corner  d). 
/.  Plowing. 

g.  Gaining. 

h.  Checking. 

/»•.  Raised  paneling. 

Specimens  of  wood  joints  are : 

I.  Mortise  and  tenon. 

m.  Tongue  and  grove,  or  matched  joint. 

n.  Dovetail. 

p.  Miter  joint. 

r.  Half  joint. 

s,  t,  u.  Scarf  joints. 

w.  Segment  work. 

x.  Stave  work. 


THE  PATTERN  SHOP 


217 


FIG.  107.— Cuts  and  Joints  used  in  Woodworking. 


218  MECHANICAL  PROCESSES 

236.  Essential  Features  of  Patterns. — A  pattern  must  serve  the 
purpose  of  making  a  mould  which,  when  filled  with  molten  metal, 
will  produce  a  casting  of  a  certain  form  and  size.    It  would  at  first 
thought  appear  that  to  serve  this  purpose  the  pattern  should  be 
made  an  exact  model  of  the  desired  casting.    This  is  true  only  for 
some  small  simple  patterns.    There  are  some  styles  of  patterns,  or 
rather  substitutes  for  patterns,  which  bear  little  if  any  resemblance 
to  the  moulds  to  be  shaped  from  them. 

The  essential  features  which  enter  into  the  making  of  patterns 
and  which  are  made  necessary  by  considerations  of  their  practical 
use  are  outlined  in  paragraphs  237  to  241  inclusive. 

237.  Shrinkage   Allowance. — Metals   contract  more   or   less   in 
cooling;  hence  when  the  molten  metal  which  fills  a  mould  begins  to 
cool,  it  also  begins  to  contract,  and  when  cold  the  casting  is  smaller 
than  the  mould.     To  obtain  a  casting  of  the  size  designated  on  the 
drawing,  its  pattern  must  be  made  slightly  larger  than  the  casting. 
This  enlargement  in  the  size  of  a  pattern  is  called  the  shrinkage 
allowance.     The  amount  of  this  allowance   varies  with   different 
metals  and  with  different-sized  castings  of  the  same  metals,  hence 
the  allowance  necessary  for  each  pattern  is  judged  more  or  less 
by  the  experience   of  the  pattern  maker.     The   usual   shrinkage 
allowances  average  about  as  follows,  viz. : 

Cast  iron    1/8  inch  per  foot. 

Heavy  brass 1/8 

Steel     3/16      "        "       " 

Thin  brass    3/16      "        "       " 

Aluminum 7/32 

Lead   7/32      " 

In  laying  out  a  pattern  from  the  drawing  the  pattern  maker 
uses  the  shrinkage  rule  for  measurements.  This  is  a  rule  which  has 
the  shrinkage  allowance  added,  as,  for  example,  a  two-foot  shrink- 
age rule  for  cast  iron  would  be  24*4  inches  long,  graduated  in 
inches  and  fractions.  Each  standard  inch  and  fraction  is  thus  in- 
creased by  an  amount  equal  to  the  shrinkage  allowance. 

Castings  which  are  to  be  machined  to  a  definite  size  must  not 
only  have  an  allowance  made  for  shrinkage,  but  a  certain  amount 


THE  PATTERN  SHOP  219 

of  extra  metal  must  be  allowed  for  finishing.  Also  that  part  of 
the  casting  which  is  uppermost  in  the  mould  frequently  has  a  still 
further  allowance  of  metal  to  contain  impurities  and  air  bubbles 
which  float  to  the  top  of  the  casting  and  may  be  imprisoned  therein 
when  the  mould  is  poured. 

The  shrinkage  allowance  for  small  castings  is  sufficiently  pro- 
vided for  by  the  rapping  given  a  pattern  to  loosen  it  when  it  is 
removed  from  the  sand  of  the  mould. 

238.  Drawing  a  Pattern  from  the  Mould. — After  the  sand  is 
packed  about  the  pattern  in  a  mould,  the  pattern  must  be  with- 
drawn before  the  mould  can  be  filled  with  metal.  In  determining 
how  a  pattern  shall  be  built,  the  first  consideration  is  to  decide 
how  it  shall  rest  in  the  mould  with  relation  to  the  joints  between 
the  parts  of  the  mould,  so  that  it  may  be  withdrawn  without  tear- 
ing the  sand.  It  is  usual  to  give  a  pattern  a  slight  taper  to  facili- 
tate its  withdrawal. 

This  taper  or  "  draft "  is  all  that  is  necessary  for  the  ready  with- 
drawal of  small  and  simple  patterns,  but  the  majority  of  patterns 
are  of  such  shapes  that  they  must  be  made  in  two  or  more  parts, 
easily  separable,  to  get  them  out  of  the  mould.  These  parts  are 
held  together  by  dowel  pins.  A  pattern  is  usually  divided  along 
its  plane  of  symmetry  into  two  parts,  and  is  so  moulded  that  this 
division  coincides  with  the  parting  of  the  mould.  A  mould  is  also 
usually  made  in  two  parts,  the  upper  of  which  is  called  the  cope 
and  the  lower  is  called  the  drag  or  nowell.  When  the  upper  part 
of  the  mould  is  lifted  away  from  the  lower  part,  the  upper  part  of 
the  pattern  is  lifted  with  it.  Each  part  of  the  pattern  can  then  be 
lifted  from  the  sand  after  a  light  rapping. 

If  either  part  of  the  pattern  has  any  projection  which  would 
tear  the  sand  in  withdrawing,  it  must  be  dowelled  in  place  in  such 
a  manner  that  it  will  be  left  behind  when  the  part  to  which  it  is 
attached  is  withdrawn,  or  else  the  mould  must  be  so  built  that 
a  section  of  it  may  be  taken  away  as  a  "  drawback  "  before  that  part 
of  the  pattern  is  lifted  out. 

Figs.  108  and  109  show  examples  of  simple  patterns  suitably 
made  for  withdrawing  from  the  moulds. 


220 


MECHANICAL  PROCESSES 


Fig.  108  shows  two  views  of  a  gland  G  to  be  cast  hollow.  The 
bolt  holes  1)  in  the  flange  and  the  taper  at  the  end  d  are  cut  in  the 
machine  shop  after  the  casting  is  made.  This  gland  is  cast  from  the 


Y/////////////////////// 

G 


FIG.  10S.— Metal  Casting  and  its  Pattern. 


FIG.  109. — A  Casting  and  its  Patterns. 

pattern  H,  placed  horizontally  in  the  mould.  The  halves  of  the 
pattern  are  separated  in  the  view  to  show  the  line  of  parting.  The 
bolt  holes  are  reinforced  by  small  raised  pieces  li,  cast  with  the 
flange.  If  these  projections  were  made  fast  on  the  pattern  they 


THE  PATTERN  SHOP 


221 


would  tear  the  sand  of  the  mould  when  each  half  of  the  pattern 
was  lifted  out  in  the  directions  of  the  arrows,  hence  they  are  held  on 
the  pattern  flange  by  small  wires  Jc  which  are  withdrawn  when 
enough  sand  has  been  rammed  against  the  flange  to  hold  the  pro- 
jections in  place.  The  pattern  may  then  be  withdrawn  from  the 
mould,  leaving  the  projections  behind,  and  these  are  drawn  out 
horizontally  into  that  part  of  the  mould  space  which  was  occupied 
by  the  flange. 

In  Fig.  109  the  moulds  B  and  C,  of  the  same  casting  A,  show  two 
methods  of  constructing  a  pattern  for  ready  w-thdrawal  from  the 
sand.  The  mould  B  is  the  simpler.  In  this  mould,  the  cope  is 


FIG.  110. — Pattern  and  Mould  of  Gear  Wheel. 

lifted,  the  parts  marked  1  are  lifted  out  together,  and  the  parts 
marked  2  and  3  are  then  removed  by  first  drawing  them  horizon- 
tally into  the  space  left  by  the  lower  part  of  1. 

In  the  mould  Cf  parts  4  and  5  are  merely  dowelled  together.  The 
cope  is  lifted,  part  4  is  lifted,  and  the  cheek  is  then  lifted,  leaving 
part  5  on  the  parting  between  the  cheek  and  the  drag.  In  a  mould 
of  three  parts,  the  middle  part  is  called  the  cheek. 

The  pattern  of  the  bevel  wheel  shown  in  Fig.  110  is  made  in  two 
parts.    The  hub  and  the  spokes  are  made  as  one  part.    The  mould 
of  the  wheel  is  parted  along  the  line  a  b  c  d  g  I  m  n  o,  so  that  the 
hub  and  spokes  will  lift  with  the  cope. 
15 


222 


MECHANICAL  PROCESSES 


239.  Core  Prints  and  Core  Boxes. — A  hollow,  recess,  or  cavity  in 
a  casting  is  usually  made  by  means  of  a  baked-sand  core.  This 
core  is  placed  in  the  mould  after  the  pattern  is  removed.  It  occu- 
pies the  space  to  be  made  hollow  and  is  surrounded  by  metal  when 
the  mould  is  poured. 

The  pattern  is  not  recessed  nor  made  hollow  to  correspond  with 
the  casting,  but,  instead,  is  made  as  shown  in  Fig.  108,  with  solid 
projections  or  core  prints  extending  from  the  part  to  be  hollowed 
out.  The  prints  in  the  figure  are  marked  m  and  n,  and  when  the 
two  parts  of  the  pattern  are  together,  the  end  view  of  each  print  is, 
in  this  case,  a  circle.  These  prints  have  the  same  axis  and  are  of 
the  same  diameter  as  the  hollow  part  of  the  casting.  The  im- 
pressions which  core  prints  make  in  the  mould  serve  as  bearings 
to  support  the  ends  of  the  core. 

The  pattern  maker  must  supply  with  the  pattern  a  core  box,  as 
in  Fig.  Ill,  in  which  the  moulder  shapes  the  core.  A  core  box  is 


FIG.  111. — Core  Box. 

usually  made  in  symmetrical  halves  for  the  purpose  of  removing  a 
core  readily  after  the  sand  composing  it  is  properly  rammed  therein. 
The  halves  are  placed  correctly  together  by  aid  of  wooden  dowel 
pins  and  the  moulder  holds  the  box  together  with  a  clamp. 

In  many  cases,  cavities  or  hollows  can  be  moulded  without  the 
aid  of  cores.  Patterns,  are  then  made,  without  core  prints,  to  the 
contour  of  the  desired  casting. 


FIG.  112. — Square  and  Filleted  Corners. 

240.  Fillets. — Sharp  angles  caused  by  the  meeting  of  surfaces  in 
different  planes  should  be  avoided  in  solid  metal  work  wherever 
possible.  A  sudden  change  in  the  direction  of  a  surface,  causing  a 


THE  PATTERN  SHOP 


223 


sharp  angle  as  at  B,  Fig.  112,  is  detrimental  to  the  strength  of  a 
casting  or  forging  in  the  angle.  This  condition  may  be  avoided 
by  making  the  change  of  direction  gradual,  as  at  (7.  In  shop  par- 
lance, the  corner  C  is  said  to  be  filleted. 

Pattern  shops  are  supplied  with  a  soft  metal  fillet  material  wound 
on  reels.  This  is  tacked  in  all  angles  of  patterns  where  fillets  are 
not  made  in  the  wood  itself  in  the  course  of  shaping  it  for  the 
pattern. 

241.  The  Prevention  of  Warping. — Intricate  patterns,  whether 
small  or  large,  must  be  made  of  several  pieces  of  wood  so  joined 
together  by  glue  that  the  tendencies  of  the  several  pieces  to  warp 
may  be  counteracted.  This  is  accomplished  by  placing  the  pieces 


FIG.  113. — Tendency  in  Warping. 

together  so  that  the  grain  of  adjacent  pieces  runs  in  different 
directions.  A  very  common  example  of  this  is  seen  in  the  segment 
work  of  Fig.  107.  Also,  it  may  in  some  cases  be  advantageous  to 
note  the  part  of  the  log  from  which  the  wood  is  cut.  The  direction 
in  which  a  board  tends  to  warp  is  shown  by  the  log  end  in  Fig.  113. 

242.  Marking  and  Preserving  Patterns. — It  is  very  essential  to 
shellac  or  varnish  wood  patterns  to  keep  them  from  absorbing 
moisture  from  the  sand  of  the  mould.  This  smooth  coating  also 
assists  in  drawing  them  from  the  mould. 

After  applying  shellac  or  varnish,  many  shops  paint  patterns  red 
for  cast-iron  castings  and  brown  for  steel  castings.  Core  prints 
and  core  boxes  are  almost  always  painted  black.  Occasionally  some 
part  of  a  pattern  is  made  merely  to  enable  the  pattern  to  be  drawn 
from  the  mould  and  is  not  to  be  reproduced  in  the  casting.  Such 


224  MECHANICAL  PROCESSES 

a  part  is  usually  striped  with  black  to  designate  to  the  moulder 
that  the  space  it  leaves  in  the  mould  is  to  be  filled  up  with  sand. 

Patterns  are  too  expensive  to  be  thrown  away  when  the  castings 
desired  are  made  from  them.  Each  pattern  should  be  marked  or 
tagged  with  a  number  and  its  name,  and  should  be  stored  in  a 
store  room  where  it  can  be  readily  found.  A  record  book  of 
patterns  is  kept  to  show,  among  other  things,  how  many  patterns 
are  in  a  complete  set  for  making,  for  example,  the  several  castings 
of  an  engine. 

243.  Pattern-Shop    Accessories    and    Methods. — Experience    in 
pattern  building  has  brought  into  use  a  number  of  helpful  appli- 
ances and  methods  which  greatly  assist  efficiency  and  rapidity  of 
work,  and  which  are  mentioned  specifically  in  this  and  the  two  para- 
graphs following. 

The  work  bench  is  the  center  of  the  pattern  maker's  activities. 
This  bench  is  particularly  designed  and  equipped  for  his  conveni- 
ence in  saving  time.  Essential  fittings  are  (1)  the  bench  vise,  (2) 
the  adjustable  bench  stop  against  which  work  is  held  for  planing, 
(3)  the  bench  hook  for  steadying  work  while  sawing,  chiseling, 
boring,  etc.,  (4)  the  miter  box  to  guide  the  saw  in  cross  cutting  a 
piece  at  angle  of  30°,  45°,  60%  or  90°  to  its  length,  and  (5)  a  rack 
at  the  back  of  the  bench  on  which  tools  can  be  placed  in  a  certain 
order  for  finding  them  readily. 

244.  The   Laying-Down   Board. — Adjacent  to   each   bench   is   a 
large  drawing  board,  about  6x8  feet  in  size,  made  of  clear  soft  wood 
of  sufficient  thickness  to  be  rigid,  and  conveniently  supported. 

When  the  pattern  maker  receives  from  the  drawing  room  a  work- 
ing drawing  from  which  a  pattern  is  to  be  made,  his  first  step,  after 
determining  the  allowances  for  shrinkage  and  finishing,  is  to  copy 
the  drawing  to  full  size  on  the  board,  marking  with  compasses  and 
steel  scriber,  and  using  the  shrinkage  rule  for  measurements. 

The  next  step  is  to  decide  how  the  pattern  shall  be  drawn  from 
the  mould,  and  then  the  method  of  putting  it  together  is  decided, 
i.  e.,  the  way  in  which  the  various  pieces  of  wood  composing  it  shall 
be  joined.  The  pattern  maker  is  now  ready  to  get  out  the  needed 
material  and  work  it  into  shape. 

245.  The   Marking-Off   Table.— The   building   of   patterns   and 
finishing  them  accurately  to  shape  is  greatly  assisted  in  many  cases 
by  a  marking-off  table.    This  is  a  flat  cast-iron  slab  about  4x6  feet 


THE  PATTERN  SHOP 


225 


surface  which  is  ribbed  underneath  for  rigidity.  It  is  mounted  as 
shown  in  Fig.  114.  The  sides  and  ends  are  at  right  angles  to  the 
top. 

Such  a  table  affords  a  level  base  for  the  purpose  of  accurate  build- 
ing up  or  measuring  a  pattern,  particularly  when  its  parts  are 
intricate. 


FIG.  114.— Marking-Off  Table. 

246.  Varieties  of  Patterns. — In  forms  of  construction,  patterns 
may  be  divided  into  three  varieties,  viz.,  (1)  solid  patterns,  (2) 
hollow  and  skeleton  patterns,  and  (3)  sweeps. 

Small  patterns  are  built  solid,  made  up  in  most  cases  of  parts  so 
glued  together  as  to  prevent  warping.  Some  large  patterns  are  also 
made  solid  for  rigidity.  Hollow  and  skeleton  patterns  and  sweeps 
are  made  to  save  expense. 


FIG.  115.— Steam  Nozzle. 

Large  hollow  patterns  may  be  built  up  of  segment  work  or  stave 
work  as  shown  in  W  and  X,  Fig.  107. 

247.  Skeleton  Patterns.— The  skeleton  pattern  is  well  adapted  to 
irregular  hollow  castings,  such  as  the  steam  nozzle  with  three  out- 
lets, a  drawing  of  which  is  shown  in  Fig.  115.  The  pattern  is  made 
in  two  parts  divided  along  the  plane  of  symmetry  AB.  In  building 


226 


MECHANICAL  PROCESSES 


this  pattern,  the  three  outlet  flanges  are  built  in  halves  of  segment 
work,  and  these  are  joined  by  skeleton  framing  made  up  as  a  back- 
bone, ribs  and  battens  for  each  half.  The  marking-off  table  may  be 
used  to  great  advantage  in  this  work. 

Fig.  116  is  a  simple  form  of  skeleton  pattern  shown  merely  to 
illustrate  the  method  of  building  and  using  this  kind  of  pattern. 
This  is  the  pattern  of  a  plain  length  of  cylindrical  pipe.  Each 
half  is  formed  of  a  backbone,  two  ribs,  and  four  battens. 

The  lower  half  of  the  pattern  is  made  so  that  the  inner-  surfaces 
of  the  backbone  and  other  parts  are  faired  to  the  contour  of  the 
inner  surface  of  the  casting,  and  the  upper  half  is  made  so  that  its 


FIG.  116. 

outer  surfaces  are  faired  to  the  contour  of  the  outer  surface  of  the 
casting.  The  battens  C  occupy  part  of  the  space  of  the  walls  of  the 
casting. 

In  making  a  mould  from  this  type  of  pattern,  the  moulder  beds 
the  lower  half  of  the  pattern  in  the  sand  of  the  lower  half  of  the 
mould,  making  the  parting  along  the  line  1,  2,  3,  4,  5. 

The  core  for  the  casting  is  then  formed  of  sand  and  other 
materials  in  the  space  enclosed  between  the  two  halves  of  the 
pattern.  The  core  is  built  up  as  far  as  can  be  done  before  placing 
the  upper  half  of  the  pattern.  When  this  half  is  placed,  the  core 
surface  is  carried  to  the  outline  of  the  semi-circle  6.  Non-plastic 
pasting  sand  is  sprinkled  over  this  surface  (as  was  done  over  the 
joints  1,  2,  3,  4,  5)  and  the  upper  half  of  the  mould  is  built  thereon. 


THE  PATTERN  SHOP  227 

When  completed,  the  upper  half  of  the  mould  is  lifted  off,  and 
the  sand  is  scraped  from  between  the  several  battens  and  backbone 
joining  the  two  end  ribs  of  the  upper  half  of  the  pattern  by  means 
of  the  small  strike  or  strickle  S,  which  scrapes  away  the  sand  to 
the  thickness  of  the  batterns  c.  The  upper  half  of  the  pattern  is 
then  lifted  away,  exposing  the  true  surface  of  the  upper  half  of 
the  core.  The  core  is  then  lifted  out,  and  the  strike  T  is  used  to 
scrape  away  the  sand  between  the  longitudinal  parts  of  the  lower 
half  of  the  pattern,  after  which  this  half  is  lifted  out. 

The  strikes  S  and  T  have  scraped  out  the  sand  which  occupied 
the  space  for  the  casting.  After  the  lower  half  of  the  pattern  is 
lifted  out,  the  mould  is  smoothed,  the  cavities  left  by  the  four  end 
ribs  are  filled  to  the  extent  needed,  and  the  core  is  replaced  in  the 
mould.  The  mould  is  now  complete,  ready  for  pouring. 

248.  Sweeps. — When  the  surface  of  a  casting,  such  as  a  steam 
cylinder,  a  propeller  blade  and  hub,  etc.,  is  wholly  or  in  its  main 
features  a  surface  of  revolution,  or  may  be  generated  by  the  revo- 
lution of  a  line  about  a  fixed  axis,  the  mould  for  such  a  casting  may 
be  formed  almost  entirely  by  the  use  of  sweeps  in  place  of  patterns. 
Such  parts  of  the  casting  as  are  not  surfaces  of  revolution  are 
moulded  from  patterns  used  in  conjunction  with  the  sweeps. 

Sweeps  are  made  up  of  pieces  of  pine  board  cut  to  such  a  profile 
that  they  will  form  the  surfaces  desired  when  revolved  on  a  vertical 
spindle  which  is  the  axis  of  revolution  of  the  casting  to  be  made. 
The  generating  edge  of  the  sweep  forms  a  surface  in  plastic  sand 
on  a  facing  of  brick  work  gradually  built  up  to  the  contour  of  this 
edge  as  the  sweep  is  moved  back  and  forth  by  the  moulder. 

Sweeps  are  used  in  making  very  large  moulds  built  of  bricks, 
known  as  loam  moulds,  and  not  for  small  moulds  made  of  sand  in 
boxes  or  flasks.  Several  SAveeps  are  required  to  make  a  complete 
set.  The  use  of  sweeps  will  be  shown  in  a  description  of  making  a 
loam  mould  in  the  next  chapter. 


CHAPTER  IX. 
THE  FOUNDRY. 

249.  The  Work  of  the  Foundry. — The  work  of  this  shop  is  divided 
principally  between  moulding  and  casting.     Moulds  are  prepared 
by  aid  of  patterns  sent  from  the  pattern  shop,  and  are  filled  with 
molten  metal  which  solidifies  to  the  more  or  less  rough  outline  of 
the  casting  desired. 

250.  Iron,  Brass  and  Steel  Foundries. — The  methods  used  in  iron 
and  brass  foundries  are  closely  associated,  and  these  two  branches 
are  usually  under  one  shop  superintendent  and  in  adjacent  build- 
ings.   The  steel  foundry  is  separate,  as  its  methods  are  enough  dif- 
ferent to  be  classed  alone. 

In  location,  it  is  highly  important  that  a  foundry  site  shall  be 
well  drained  and  without  an  excess  of  sub-surface  moisture.  Large 
moulds  must  be  bedded  in  pits  8  or  10  feet  deep  to  secure  them  for 
withstanding  the  great  pressure  of  a  large  bulk  of  molten  metal.  If 
the  soil  over  which  the  foundry  is  built  is  not  a  loose  sand  or  loam, 
it  must  be  dug  out  to  a  depth  of  several  feet  where  large  moulds 
are  to  be  bedded  and  filled  in  with  friable  earth  not  pasty  with  an 
excess  of  clay. 

251.  Classes    of    Moulds. — There    are    four    general    classes    of 
moulds,  designated  as  follows : 

(1)  Open  sand  moulds.          (3)   Dry  sand  moulds. 

(2)  Green  sand  moulds.          (4)   Loam  moulds. 

Open  sand  moulds  are  the  cheapest  class  of  moulds.  They  are 
merely  depressions  made  in  a  carefully  leveled  bed  of  sand  in  the 
foundry  floor.  The  upper  surface  of  the  casting  remains  exposed 
to  the  air  when  poured.  Only  rough  castings,  flat  on  top,  for 
foundry  uses,  are  made  in  open  sand  moulds. 

Green  sand  moulds  are  so  called  because  they  are  moulds  in  damp 
sand,  not  baked  or  dried.  They  are  the  cheaper  class  of  moulds, 
and  are  usually  made  in  wooden  flasks.  With  increased  skill  in 
moulding  they  are  now  extended  to  embrace  moulds  for  large  and 


THE  FOUNDRY 


229 


somewhat  complicated  castings,  thus  reducing  the  cost  of  produc- 
tion. The  greater  part  of  the  castings  of  commercial  objects  are 
made  in  green  sand. 

Dry  sand  moulds  are  virtually  green  sand  moulds  carefully  made, 
generally  in  iron  flasks,  and  dried  in  a  mould  oven  to  make  the  sand 
firmer  and  more  stable.  This  class  of  moulds  is  used  for  castings 
which  have  a  complex  form,  and  which  must  be  smooth,  sound, 
correct  in  shape,  and  free  from  internal  strains.  Superior  castings 
are  produced  by  this  method,  and  the  cost  is  about  1.5  times  the 
cost  of  similar  castings  from  green  sand  moulds.  A  dried  mould 
surface  can  be  given  a  very  smooth  finish,  producing  very  smooth 
castings. 


FIG.  117.— An  Open  Sand  Mould. 

Loam  moulds  are  used  for  large  complicated  and  important  cast- 
ings, such  as  large  steam  cylinders,  propeller  blades,  etc.  A  loam 
mould  is  built  of  bricks  on  large,  flat,  rigid,  cast-iron  plates.  The 
bricks  of  these  moulds  are  faced  with  loam  to  form  the  mould 
surface. 

Loam  and  dry  sand  castings  are  about  the  same  in  quality,  and 
the  relative  expense  of  the  two  kinds  of  moulding  depends  upon 
the  shape  of  the  casting  and  the  quantity  to  be  made. 

252.  Example  of  an  Open  Sand  Mould. — Fig.  117  shows  an  open 
sand  mould  in  course  of  preparation.  This  is  very  simple  and  de- 
mands no  particular  skill.  Two  boards,  A  and  B,  are  imbedded  on 
edge  in  the  foundry  floor  and  are  leveled  along  their  length  and 
across  from  one  to  the  other.  The  sand  between  them  is  tamped 


230 


MECHANICAL  PROCESSES 


down  and  leveled  off  by  a  straight-edged  board  drawn  along  A  and 
B,  and  a  tracing  of  the  plate  to  be  cast  is  marked  on  this  bed  of 
leveled  sand.  The  outer  edge  and  the  center  core  of  the  mould  are 
formed  by  pressing  damp  moulding  sand  with  the  hand  firmly 
against  wooden  segments  made  to  the  necessary  curvature.  The 
center  core  will  core  a  hole  in  the  center  of  the  plate,  and  smaller 
holes  may  be  cored  anywhere  desired  in  the  plate  by  small  baked 
cores  C,  C,  which  are  kept  from  floating  or  washing  out  of  position 
by  convenient  weights,  as  at  D.  Lifting-lugs  are  provided  at  the 
edges  of  the  plate.  This  is  a  type  of  plate  frequently  used  to  form 
the  top  of  a  loam  mould.  Small  projections  or  prickers  are  usually 


FIG.  118. — Example  of  a  Small  Green  Sand  Mould. 

cast  on  the  under  side  of  the  plate  to  assist  in  holding  the  loam 
coating  which  the  plate  must  carry  as  a  part  of  a  loam  mould 
surface.  Impressions  are  made  for  these  prickers  by  sticking  holes 
in  the  sand  with  a  small  stick,  or  the  prickers  may  be  formed  by 
sticking  two-inch  nails  in  the  bottom  of  the  mould  so  that  metal 
poured  in  the  mould  will  solidify  about  the  nail  heads. 

253.  Example  of  a  Green  Sand  Mould. — Fig.  118  shows  a  typical 
small  green  sand  mould  in  a  two-part  flask.  This  is  a  mould  of 
the  pattern  shown  in  Fig.  108.  The  upper  half  of  the  mould  is  the 
cope  and  the  lower  half  is  the  drag  or  nowell.  The  two  parts  of  the 
mould  are  separated  at  the  parting.  The  casting  is  made  hollow 
by  the  core,  resting  in  its  bearings.  A  number  of  vents  are  punched 
by  a  small  steel  wire  before  the  pattern  is  removed.  The  vents  con- 


THE  FOUNDRY  231 

duct  away  gas  and  steam  generated  in  the  sand  by  hot  metal,  and 
prevent  the  escape  of  these  into  the  mould.  Before  pouring,  the 
mould  is  weighted  down  to  keep  the  cope  from  floating.  Metal 
is  poured  from  a  ladle  into  the  'basin,  entering  the  mould  through 
the  runner  and  gate.  Many  moulders  designate  the  runner  as  the 
sprue.  As  pouring  continues,  metal  gradually  fills  the  mould  and 
rises  to  the  top  of  the  riser.  Vent  gases  escape  at  the  top,  around 
the  parting  and  along  the  bottom  board.  Air  escapes  from  the 
mould  cavity  through  the  riser  as  metal  is  poured  in:  A  small  vent 
channel  runs  through  the  core,  conducting  gases  to  the  parting.  A 
single  flask  often  contains  several  moulds  of  small  castings,  all  run 
from  the  same  sprue. 

254.  Essential  Features  of  a  Mould. — All  moulds,  whether  for 
steel,  iron  or  brass,  must  fulfill  the  following  general  requirements, 
viz. : 

(1)  They  must  be  made  so  that  the  pattern  can  be  removed 
readily  therefrom. 

(2)  Not  only  must  an  opening  be  made  in  the  sand  for  pouring 
metal  into  the  mould,  but  a  riser  hole  must  lead  upward  through 
the  sand  from  each  of  the  high  parts  of  the  mould  cavity.     This 
serves  (a)  to  keep  air  from  being  imprisoned  in  the  mould  when 
metal  is  poured  in;  (b)  to  allow  for  loose  sand  and  scum  on  the 
metal  to  float  out,  and  (c)  to  provide  a  bulk  of  hot  metal  to  "  feed  " 
the  casting  as  it  shrinks  in  solidifying. 

(3)  A  mould  must  resist  burning  and  crumbling  when  filled 
with  molten  metal,  and  must  resist  bursting  from  the  static  pres- 
sure of  the  metal. 

The  requisite  qualities  of  sand  for  moulds  will  be  mentioned  later. 

255.  Foundry  Equipment. — The  main  equipment  of  the  foundry 
may  be  stated  as  follows : 

(1)  Moulding  sands  in  bins,  and  other  moulding  materials. 

(2)  Flasks  in  which  moulds  are  made. 

(3)  Moulders'  tools  and  accessories  used  in  making  moulds. 

(4)  One  or  more  traveling  cranes  equipped  with  various  lifting 
and  transporting  appliances. 

(5)  Usually  two  or  more  cupolas  for  melting  pig  and  scrap 
cast  iron. 


MECHANICAL  PROCESSES 


THE  FOUNDRY  233 

(6)  A  reverberatory  oil  or  coal  furnace  for  melting  bronze  or 
brass  for  large  castings. 

(7)  A  crucible  furnace  for  melting  brass. 

(8)  Ladles  for  holding  molten  metals. 

( 9 )  A  drying  room  or  "  oven  "  for  drying  dry  sand  and  loam 
moulds. 

(10)  A  core  oven  for  drying  or  "baking"  cores. 

(11)  Equipment  for  cleaning  castings,  as  wire  brushes,  emery 
wheel,  and  tools  for  cutting  fins  and  other  refuse  parts  from  cast- 
ings, tumbling  barrels,  etc. 

Moulding  machines  are  used  to  make  small  moulds  in  foundries 
which  turn  out  duplicate  work.  There  are  several  subsidiary 
machines  for  foundry  use,  such  as  sand  mixers,  clay  grinders,  etc., 
but  these  are  not  universally  needed.  Fig.  119  shows  a  view  of  a 
moulding  floor  of  a  foundry. 

256.  Moulding-  Sand. — This  is  the  most  important  of  the  mould- 
ing materials.  In  different  forms,  it  has  different  uses  and  is  given 
different  names,  such  as  green  sand,  loam,  facing  sand,  core  sand, 
brass  sand.  All  moulding  sands  are  essentially  mixtures  of  silica 
to  give  porosity  and  clay  to  give  tenacity.  Silica  grains  are  re- 
fractory and  have  no  cohesion.  Clay  is  a  fine  powder,  is  refractory 
and  when  wet  is  adhesive  and  plastic.  These  two  ingredients  are 
mixed  in  different  proportions,  the  silica  grains  varying  in  size,  to 
make  mixtures  suitable  for  different  uses. 

"Other  materials  are  mixed  with  moulding  sands  for  various  pur- 
poses, as  will  be  mentioned. 

All  moulding  sand  mixtures  are  more  or  less  wet  when  formed 
into  moulds.  The  requirements  of  a  good  moulding  sand  are : 

(a)  Sufficient  porosity  to  allow  the  escape  of  gas  and  steam  gen- 
erated in  the  body  of  the  mould  by  the  heat  of  the  molten  metal. 
The  greater  the  bulk  of  metal  the  coarser  the  sand  used,  and  the 
greater  the  need  for  careful  venting. 

(b)  Sufficient  plasticity  and  tenacity  to  hold  its  form  in  the 
mould  and  to  resist  the  erosive  action  of  hot  metal.    These  qualities 
are  due  to  clay,  which  is  more  or  less  detrimental,  because  it  fills 
the  spaces,  or  pores,  between  the  silica  grains. 

(c)  A  high  enough  fusing  point  not  to  melt  and  stick  to  the  face 
of  the  casting-. 


234  MECHANICAL  PROCESSES 

There  are  many  trade  names  for  foundry  sands,  but  all  must  ful- 
fill the  requirements  mentioned.  Vegetable  or  other  combustible 
matter,,  sea  salt,  lime,  and  substances  easily  decomposed  by  heat 
should  not  exist  naturally  in  moulding  sand,  as  they  may  cause 
failure  in  casting. 

Brass  sand  is  green  sand  of  fine  grain  used  in  moulds  for  brass 
castings. 

Facing  sand  is  also  a  fine-grained  sand  placed  next  to  the  pattern 
in  small  moulds  to  make  a  smooth  casting. 

Core  sand  is  used  for  cores. 

Loam  is  a  very  course  moulding  sand  made  up  for  loam  moulds. 

257.  Other  Materials  Used  in  Moulding. — Designating  moulding 
sand  as  first  on  the  list,  other  important  moulding  materials  are 
named  as  follows : 

(2)  Fire  clay  is  a  pure  clay  (oxide  of  aluminum)  much  used  when 
mixed  with  water  as  a  plastic  refractory  material  for  patching  ladle 
and  cupola  linings,  and  for  use  in  moulding. 

(3)  Clay  wash  or  clay  water  is  a  thin  mixture  of  fire  clay  and 
water.     It  is  added  to  moulding  sand  mixtures  (particularly  loam 
mixtures)  to  give  them  the  necessary  plasticity.     It  is  also  used  to 
wet  sticks,  nails,  iron  rods,  core  irons,  etc.,  imbedded  in  moulds  and 
cores  to  make  sand  adhere  to  them,  thus  strengthening  the  body  of 
the  mould. 

(4)  Common  red  bricks  are  used  to  make  the  body  of  loam 
moulds  and  to  fill  up  remote  spaces  in  large  dry  sand  moulds.    They 
are  piled  evenly  in  the  spaces  they  occupy,  and  afford  porosity. 

(5)  Parting  sand  is  sprinkled  on  the  joints  or  partings  of  moulds, 
as  between  the  cope  and  the  drag,  to  keep  the  two  parts  of  the  mould 
from  sticking  at  the  joint.     Any  fine-grained  non-plastic  material, 
such  a  brick  dust,  silica  sand,  ground  cinders,  etc.,  may  be  used. 

(6)  Slurry  js  clay  wash  and  fine  moulding  sand  mixed  thick. 
It  is  used  as  the  first  smooth  coating  over  the  rough  loam  surface 
of  a  loam  mould. 

(7)  Cinders  from  completely  burned  coal  are  used  in  venting  to 
assist  the  porosity  of  large  cores  and  sand  projections  in  moulds, 
and  are  placed  under  large  moulds  to  receive  and  convey  gases  from 
the  moulds. 


THE  FOUNDRY  235 

(8)  Blacking  and  sleeking  mixtures  are  used  as  a  final  smooth 
coating  over  the  surface  of  a  mould  after  the  pattern  is  withdrawn. 
These  are  known  as  mould  facings,  facing  mixtures,  etc.     They 
give  a  smooth  surface  to  the  casting.     Some  mixtures  contain  mo- 
lasses, stale  beer,  or  other  viscous  substances,  to  prevent  the  sand  of 
the    mould    washing   away    when    metal    is    poured.      Facings    of 
powdered  slaty  coal,  charcoal,  graphite,  soapstone,  or  ground  silica, 
are  dusted  on  the  faces  of  green  sand  moulds  from  small  muslin 
bags.    These  are  applied  wet,  with  a  brush,  to  dry  sand  and  dried 
loam  moulds,  and  are  slicked  when  nearly  dry  to  make  a  smooth 
glossy  surface. 

(9)  Flour,  stale  beer,  oil,  and  molasses  are  used  to  increase  the 
tenacity  of  sand  in  moulds.     A  more  important  feature  of  flour  is 
that  it  chars  when  metal  is  poured  into  the  mould,  allowing  core  sand 
to  disintegrate  and  crush  as  the  casting  contracts  in  cooling.    Flour 
paste  and  putty  are  used  to  make  a  tight  joint  between  a  core  and  its 
bearing. 

(10)  Oil  is  used  to  coat  large  patterns  in  loam  moulding  to  keep 
the  loam  from  sticking  to  the  pattern. 

(11)  Loose  or  chopped  straw  and  dry  horse  manure  are  used  in 
loam  moulds  to  increase  porosity,  and  straw  rope  is  wound  on  "  core 
barrels,"  or  large  metal  pipes,  which  are  then  covered  with  loam  and 
dried  for  use  as  cores  for  moulding  large  water  and  gas-main  piping. 

The  moulder  applies  "the  name  of  sharp  sand  or  fire  sand  to  silica 
or  any  other  kind  of  gritty,  non-adhesive  sand.  Burnt  sand  is  a 
sand  which  has  lost  its  tenacity  by  having  been  highly  heated  next  to 
a  casting  in  the  mould.  Burnt  sand  must  have  new  sand  mixed  with 
it  to  fit  it  for  moulding,  though  the  worst  of  it  is  thrown  away. 

Loose  sand  and  refuse  must  not  be  allowed  to  accumulate  about 
the  foundry  floor. 

It  will  be  seen  that  many  of  these  materials  are  to  assist  one  or 
more  of  the  three  essentials,  a,  b,  c,  mentioned  in  the  preceding 
paragraph,  for  moulding  sands. 

258.  Flasks  for  Green  and  Dry  Sand  Moulds.— Moulds  of  these 
two  classes  are  made  in  flasks  of  various  shapes  and  sizes.  Wood  or 
iron  flasks  are  used  for  green  sand  molds  and  cast-iron  flasks  are 
used  for  dry  sand  and  steel  moulds. 


236 


MECHANICAL  PROCESSES 


Fig.  120  shows  three  flasks  extensively  used  for  small  moulds. 
Each  of  these  consists  of  three  parts — cope,  drag  and  bottom  board. 
Suitable  lugs  and  pins  are  provided  to  insure  the  cope  and  the  drag 
going  together  always  in  the  same  relative  position.  No.  2  may  be 
poured  from  the  top,  or  may  be  set  on  end  and  poured  through  one 
of  the  holes  in  the  end  to  insure  a  better  metal  pressure  in  the 
mould.  No.  1  is  a  snap  flask,  which  may  be  removed  from  a  mould 
and  used  for  making  other  moulds  of  the  same  size.  When  this 
flask  is  removed,  a  rectangular  box  is  slipped  over  the  mould  in  its 
place  to  support  the  sand.  No.  3  is  for  general  use  for  small  moulds. 
Each  size  of  small  flasks  for  general  use  should  1 3  made  inter- 
changeable, i.  e.,  the  upper  part  of  any  flask  should  fit  the  lower  part 
of  any  other  flask. 


FIG.  120. — Small  Moulding  Flasks. 

Fig.  121  shows  two  flasks  for  medium-sized  moulds.  The  weight 
of  sand  in  the  cope"  is  too  great  to  hold  in  place  without  the  cope 
bars  B.  The  drag  needs  no  bars,  but  it  must  have  a  bottom  board 
if  it  is  to  be  turned  over  in  the  course  of  making  the  mould. 

The  upper"  view  shows  a  three-part  flask  for  a  pattern  which  can- 
not be  removed  from  a  single  parting  in  the  two-part  flask.  The 
cheek,  or  middle  part  of  the  flask,  also  has  bars.  These  extend 
radially  from  corners  and  sides  of  the  cheek  toward  the  pattern,  but 
bars  should  not  be  within  less  than  about  %  inch  of  the  pattern 
surface. 

Many  cast-iron  flasks  are  shown  in  the  view  in  Fig.  119.  They 
are  made  up  of  flat  cast-iron  sections  bolted  together,  or  of  round 
sections  made  in  one  piece.  A  large  cope  is  shown  at  C  with  rods 
and  bars  arranged  for  a  particular  casting.  A  circular  cope  and 
drag  clamped  together  are  marked  B  and  D.  Each  of  these  parts 


THE  FOUNDRY 


237 


has  a  pair  of  trunnions  by  which  it  may  be  suspended  and  re- 
volved while  giving  the  mould  its  finishing  touches. 

Several  minor  devices  are  used  for  assisting  cope  bars  to  hold  a 
body  of  sand  firmly  in  place.  Nails  are  frequently  driven  along 
the  under  edge  of  a  bar  to  hold  projections  of  sand  in  an  irregularly 
shaped  parting.  Bent  iron  rods,  called  gaggers,  are  imbedded  in  the 


FIG.  121.— Moulding  Flasks. 

sand  to  anchor  the  unstable  parts  to  the  firmer  bodies  of  sand  in  a 
cope  or  a  cheek.  Small  tapered  sticks,  called  soldiers,  are  used  when 
the  mould  is  delicate  and  cannot  stand  the  weight  of  gaggers. 

Loose  nails  are  often  imbedded  in  corners  of  sand  or  are  stuck 
in  the  surface  of  a  mould  to  hold  the  sand  firmly  against  breaking 
or  wearing  away  by  erosion.     Gaggers,  nails,  etc.,  are  wet  with  clay 
water  to  make  the  sand  stick  to  them. 
16 


238 


MECHANICAL  PROCESSES 


259.  Tools  Used  in  Moulding. — The  moulder's  tool  kit  is  simple 
and  includes  articles  of  the  following  list,  most  of  which  are  shown 
in  Fig.  122 : 

(1)  Vent  wire  for  sticking  vent  holes  through  the  sand  of  the 
mould. 

(2)  Pattern  lifter. 

(3)  Joint  trowel  and  (4)  heart  trowel  for  smoothing  and  finish- 
ing the  parting  and  flat  surfaces  of  the  mould. 

(5)   Gate  cutter  and  pattern  lifter. 


FIG.  122.— Moulding  Tools. 

(6)  Slick  and  oval  spoon  for  finishing  mould  surfaces. 

(7)  (8)   Sand  lifters  and  slicks. 

(9)  Yankee  heel  lifter  and  flat  slick. 

(10)  Flange  and  bead  slick. 

(11)  Corner  slick. 

(12)  Edge  slick. 

(13)  Round  corner  slick. 

(14)  Pipe  slick. 

(15)  Button  slick. 
(16.)  Oval  Slick. 

(17)   Hand  rammer  for  ramming  sand  in  flasks  (not  shown). 


THE  FOUNDRY  239 

(18)   Spirit  level  for  leveling  open  sand  moulds  (not  shown). 

The  slickers  are  used  for  finishing  the  surface  of  the  mould  after 
it  has  been  dusted  or  painted  with  mould  facing. 

Additional  equipment,  usually  a  part  of  the  foundry  outfit,  in- 
cludes : 

( 1 )  Small  bellows  for  blowing  loose  sand  from  moulds. 

(2)  Sieves  (riddles)  for  sifting  sand. 

(3)  Brushes  for  applying  liquid  mould  facing  and  for  dusting 
moulds. 

(4)  Small  bags  for  dusting  dry  mould  facing. 

(5)  Heavy  and  pneumatic  rammers  for  ramming  sand  in  flasks. 

(6)  Larger  hand  tools,  as  spades,  picks,  hoe,  rake,  hand  spikes, 
crow  bars,  wrenches,  buckets  and  sprinklers. 

260.  Example  of  Making  a  Small  Mould. — The  work  of  making 
a  mould  of  the  pattern  in  Fig.  108  is  here  given  briefly  to  show  the 


PIG.  123. 

essential  steps  in  sequence.  This  is  applicable  in  general  to  green 
sand  and  dry  sand  work.  The  completed  mould  is  shown  in  Fig. 
118. 

Having  selected  a  suitable  flask,  place  one-half  of  the  pattern  on 
the  bottom  board,  as  shown  in  Fig.  123.  Place  the  drag  bottom  side 
up  on  the  board,  and  sift  about  a  half  inch  of  facing  sand  over  the 
surface  of  the  pattern,  then  fill  the  drag  heaping  full  from  the  pile 
of  moulding  sand,  sifting  part  of  it  in.  Earn  this  sand  down  firmly, 
but  not  too  hard,  and  level  it  off  even  with  the  top  edge  of  the  flask 
by  rubbing  the  sand  surface  with  another  bottom  board,  then  lift  the 
board  and  use  the  vent  wife  to  probe  several  vent  holes  which  will 
reach  all  parts  of  the  pattern's  surface.  Dig  down  with  the  small 
trowel  carefully  until  the  wires  aa  can  be  reached  and  drawn  out. 
Replace  this  sand  and  probe  a  few  vent  holes  through  it.  Replacing 
the  upper  bottom  board,  turn  the  drag  over  and  remove  the  other 
board,  which  is  now  on  top. 


240 


MECHAXICAL  PROCESSES 


The  drag  now  rests  right  side  up,  as  shown  in  Fig.  124.  Place 
the  cope  and  the  other  half  of  the  pattern  in  position,  as  shown,  and 
stick  a  riser  stick  R  slightly  into  the  sand,  about  2  inches  from  the 
pattern.  Sprinkle  a  layer  of  parting  sand  over  the  parting  to  keep 
the  sand  of  the  cope  and  that  of  the  drag  from  sticking  together. 
The  cope  is  now  filled,  rammed,  and  otherwise  prepared,  as  was 
described  for  the  drag.  The  riser  stick  S  is  placed  on  the  upper 
edge  of  the  flange  when  there  is  enough  sand  in  the  cope  to  hold  it 
up,  and  both  sticks  are  withdrawn  after  the  cope  is  vented. 

When  the  cope  is  rammed  and  vented,  lift  it  from  the  drag  and 
remove  the  pattern  by  using  the  lifting  screw.  Eap  it  a  few  times 
to  loosen  the  pattern  before  lifting.  A  little  water  squeezed  from  a 
swab  around  the  edges  of  the  pattern  will  help  hold  the  sand  in 


FIG.  124. 

place.  .Patch  the  broken  corners  of  the  mould,  cut  the  gate  with  a 
piece  of  bent  tin,  lift  out  any  loose  sand,  and  dust  the  mould  sur- 
face with  graphite  or  other  dry  facing. 

In  the  meantime  the  core-maker  makes  the  core.  The  core  box, 
shown  in  Fig.  Ill,  is  clamped  and  gradually  rammed  full  of  core 
sand.  Two  wires  are  rammed  in  with  the  sand  along  the  axis  of  the 
core.  One  of  these  remains  in  the  core  to  strengthen  it,  and  the 
other  is  removed  when  the  core  is  rammed  up  to  leave  a  vent  hole. 

The  core  must  be  carefully  removed  from  the  box.  It  rests  on 
some  loose  sand  placed  on  an  iron  plate,  and  is  slowly  baked  in  the 
core  oven.  Cores  are  usually  sprinkled  with,  molasses  water  to  make 
them  more  flinty  when  baked. 

When  the  core  is  taken  from  the  oven  and  cleaned,  it  is  placed  in 
its  bearings  in  the  drag,  and  the  mould  is  closed  and  weighted  ready 
for  pouring. 


THE  FOUNDRY  241 

261.  Moulding  Machines. — These  machines  are  profitably  em- 
ployed in  foundries  which  make  a  great  number  of  small  duplicate, 
castings.     They  are  designed  and  built  to  repeat  certain  motions 
and  operations  which  occur  in  the  work  of  moulding  all  small  cast- 
ings.    Each  machine  is  operated  by  a  workman  who  directs  the 
machine  and  who  performs   those   steps   in  the   work  which  the 
machine  cannot  perform. 

There  are  two  types  of  moulding  machines,  known  as  the  vibrator, 
and  the  squeezer. 

Snap  flasks  of  special  design  and  uniform  sizes  are  used  with 
these  machines. 

Moulding  machines  do  not  require  skilled  labor  to  operate  them, 
and  many  small  patterns  may  be  moulded  in  a  single  flask. 

262.  Cores. — Cores  are  more  or  less  surrounded  by  molten  metal 
and  are  therefore  subjected  to  more  concentrated  heat  than  other 
parts  of  the  mould.     To  serve  their  purposes  they  must  be  made 
especially  (1)   to  resist  erosion  from  flowing  metal,   (2)  to  resist 
fusing,  and  (3)  to  allow  the  escape  of  air,  steam  and  carbon  gases 
contained  in  the  core. 

Clean  silica  sand  of  more  or  less  coarse  grain  is  the  principal 
material  of  cores.  About  15%  of  flour  is  mixed  with  this  and  the 
mass  is  wet  with  thick  clay  wash  until  the  sand  grains  stick 
together. 

All  cores  must  be  carefully  vented  to  assist  the  natural  porosity 
of  the  sand.  Vent  holes  are  usually  formed  by  straight  wires. 
Crooked  vent  holes  are  formed  by  greased  strings.  Vent  wires  and 
strings  are  pulled  out  before  the  core  is  taken  from  the  core  box. 
Large  cylindrical  cores  may  be  made  in  halves  for  better  venting, 
and  all  large  cores  contain  cinders  at  the  center  to  increase  porosity. ; 
All  vents  must  lead  to  the  core  bearings  from  which  gases  escape 
along  the  mould  parting  or  through  especially  provided  pipes  or 
channels. 

Small  cores  are  strengthened  by  wires.  Specially  made  core  irons 
are  enclosed  in  large  cores  to  make  them  rigid  enough  for  handling, 
and  to  support  them  in  the  mould. 

The  baking  of  cores  makes  the  sand  much  firmer,  and  decreases 
the  gases  and  moisture  in  them.  Baking  is  usually  necessary,  but 
there  are  many  shapes  of  cores  which  can  be  made  of  green  sand  as 


24:2  MECHANICAL  PKOCESSES 

a  part  of  the  mould.  These  are  well  vented  and  are  well  enough 
supported  to  avoid  the  necessity  of  baking. 

Large  cores  for  loam  moulds  are  built  of  bricks  and  surfaced  with 
loam  and  slurry. 

For  smoothness  of  surface,  cores  are  blacked  and  slicked.  This 
is  done  after  drying. 

263.  Chaplets. — There  are  many  cases  in  moulding  in  which  a 
core  is  not  adequately  supported  by  its  bearings  in  the  sand  of  the 
mould,  particularly  if  it  has  but  one  bearing  or  is  not  a  straight  core. 

It  is  the  practice  in  these  cases  to  support  the  core  by  pieces  of 
metal  called  chaplets,  placed  in  the  mould  space.  When  metal  is 
poured  into  the  mould  around  the  chaplets,  they  soften  and  become  a 
part  of  the  casting. 


/  2 

FIG.  125. — Chaplets. 

Fig.  125  shows  four  of  the  many  shapes  of  chaplets  much  used. 
These  are  of  iron  or  brass  as  may  be  needed.  Chaplets  must  be 
cleaned  before  placing  them  in  a  mould.  They  are  often  tinned. 

It  is  frequently  necessary  to  place  a  chaplet  above  a  core  to  keep 
the  metal  from  floating  the  core  out  of  position,  beside  placing  a 
chaplet  under  the  core  to  support  it  before  the  metal  is  poured  in. 

There  will  be  noticed  often  on  the  outer  surfaces  of  hollow-cast 
pipe  elbows,  cone-shaped  projections  or  rough  spots  which  mark  the 
position  of  chaplets. 

Chaplets  are  sometimes  used  in  narrow  mould  spaces  to  insure 
the  required  thickness  of  metal  in  the  casting. 

264.  Chill  Moulds. — Surfaces  of  cast-iron  castings  subjected  to 
constant  wear,  such  as  car-wheel  rims,  anvil  faces,  and  vehicle 
wheel  boxes,  are  chilled  to  render  them  hard  and  tough.  The  chill- 
ing is  done  by  sudden  cooling  of  the  molten  iron  when  it  is  poured 


THE  FOUNDRY 


243 


into  the  mould.  A  part  of  the  mould  is  formed  of  a  piece  of  iron, 
and  when  the  molten  metal  comes  in  contact  with  this,  its  surface 
is  quickly  cooled. 


FIG.  126.— Chill  for  a  Mould. 


Fig.  126  shows  a  chill  for  a  car  wheel.  This  forms,  the  cheek  of 
a  three-part  flask.  Chills  are  made  of  cast  iron  or  cast  steel. 

265.  Example  of  a  Loam  Mould. — Fig.  127  shows  a  cross-section 
of  a  loam  mould,  with  the  parts  assembled  and  bound  together 


FIG.  127. — Loam  Mould. 


firmly.  It  is  now  ready  to  be  lowered  into  a  pit  dug  in  the  foundry 
floor  and  surrounded  by  sand  packed  inside  a  circular  curbing  of 
iron  plates  to  fortify  the  sides  against  the  pressure  of  the  molten 


244 


MECHANICAL  PROCESSES 


metal  when  poured.  Fig.  128  shows  a  drawing  of  the  cylinder  for 
which  this  mould  is  made. 

Loam  moulds  are  used  only  for  the  largest  castings,  particularly 
large  propellers  and  steam  cylinders.  The  bricks  of  these  moulds 
may  be  used  many  times. 

The  mould  here  shown  is  made  in  three  detachable  parts  carried 
on  the  heavy  cast-iron  plates  B,  D  and  T.  The  bricks  are  laid  in  a 
mortar  of  old  moulding  sand  and  water.  Venting  is  aided  by  plac- 
ing cinders  between  bricks,  and  by  mixing  chopped  straw  or  dry 
horse  manure  with  the  loam. 


FIG.  128. — Cylinder  to 
be  Moulded. 


FIG.  129. — Beginning  a  Loam  Mould. 


266,  Building  a  Loam  Mould. — Each  of  the  detachable  parts  of  a 
loam  mould  is  so  built  on  its  own  plate  that  it  can  be  handled  sepa- 
rately from  the  other  parts. 

The  mould  is  begun  by  leveling  the  heavy  foundation  plate  B 
(Fig.  129)  on  firm  supports,  and  supporting  the  spindle  8  vertically 
in  its  bearings  in  which  it  is  free  to  turn.  Sweep  No.  1,  with  edges 
iron  bound  to  prevent  wear  from  the  rough  loam,  is  then  bolted  to 
the  strap  A.  The  foundation  brickwork  C  is  built  up  with  this 
sweep  as  a  guide,  and  about  half  an  inch  of  loam  is  swept  evenly 
over  the  top  of  the  brickwork  by  revolving  the  sweep  about  the 
spindle.  This  loam  facing,  shown  in  Fig.  130,  is  allowed  to  dry  and 
the  joint  JJ  is  well  oiled. 

The  next  part  of  the  mould,  the  main  body  (marked  GG  in  Figs. 
127  and  131),  is  swept  up  on  the  lifting  ring  D  by  using  sweeps  2 


THE  FOUNDRY 


245 


and  3.  The  steps  of  this  work  are  shown  in  Figs.  130  and  131. 
The  lifting  ring  is  bedded  in  a  layer  of  wet  loam  spread  over  the 
joint  JJ.  This  loam  sticks  to  the  ring  when  dry  and  is  lifted  with  it. 
Sweep  No.  2  merely  sweeps  the  temporary  brickwork  FF,  which  is 


FIG.  130. — Sweeping  up  Dummy  Flange. 

loam  coated  to  serve  as  a  pattern  against  which  the  lower  part  of 
the  main  body  is  built.  The  revolving  of  the  sweeps  as  the  bricks 
are  placed  serves  as  a  guide  in  placing  them,  and  after  the  brick- 
work is  done,  the  loam  coating  is  plastered  on  by  hand  and  swept 


FIG.  131. — Sweeping  up  Main  Wall. 

to  shape  on  the  brick  surface  to  form  the  surface  of  the  mould,  which 
is  later  made  very  smooth. 

Any  part  of  the  casting,  as  the  nozzle  of  the  cylinder  in  Fig.  128, 
which  projects  beyond  the  surface  of  revolution,  is  moulded  by  bed- 
ding suitable  wooden  patterns  of  these  parts  in  the  brickwork.  The 
pattern  H9  with  its  core  print  P  (Fig.  131)  and  its  detachable 


246 


MECHANICAL  PROCESSES 


flange,  is  surrounded  by  a  loam  coating  as  it  is  built  in  the  wall  of 
the  mould.  These  patterns  are  removed  after  the  mould  is  lifted 
apart. 

When  sweep  No.  3  has  completed  its  work,  as  shown  in  Fig.  131, 
the  main  part  is  lifted  away  on  its  lifting  ring  D,  the  temporary 
work  FF  is  torn  away,  and  the  main  core  K,  for  making  the  cylin- 
der hollow,  is  swept  up  as  shown  in  Fig.  132.  L  is  a  small  core 
print  for  the  nozzle  core,  and  R  is  a  flat  bar  of  cast  iron  imbedded 
in  the  core.  The  bar  is  removed  just  after  the  cylinder  is  cast,  by 
digging  down  to  its  end  and  attaching  the  crane  thereto.  This  re- 


FIG.  132. — Sweeping  up  Main  Core. 

moval  allows  the  casting  to  crush  the  core  sufficiently  in  contracting 
to  avoid  cracking. 

The  assembled  mould  in  Fig.  127  shows  the  top  plate  TT  placed 
over  the  oiled  joint  EE.  Loam  has  been  swept  on  the  under  side 
of  this  plate  and  after  the  parts  of  the  mould  are  assembled  and 
bound,  the  riser  and  pouring  basins  are  shaped  of  green  sand  held  in 
place  by  the  sheet-iron  ring  V  and  the  heavy  tube  Q.  The  four- 
armed  cross  M,  resting  on  distance  pieces  Q  and  SS,  is  bound  to  the 
foundation  plate  B  as  shown. 

The  parts  of  the  mould  are  dried  after  they  are  swept  up  and 
lifted  apart.  This  is  done  in  a  large  brick  oven  and  requires  about 
60  hours.  Before  finally  assembling,  the  mould  surfaces  are  painted 
with  a  liquid  mould  facing  and  carefully  slicked  by  hand  slickers. 


THE  FOUNDRY  247 

267.  The  Cupola. — Pig  and  scrap  iron  for  castings  are  generally 
melted  in  a  cupola,  although  a  reverberatory  furnace  may  be  used. 
Fig.  133  shows  a  typical  cupola  in  cross-section.     A  cast-iron  or 
cast-steel  base  ring  B  is  supported  about  3  feet  from  the  ground  by 
four  iron  posts  C.    This  ring  carries  a  shell  D  of  steel  plates  lined 
inside  with  refractory  bricks.     The  top  of  the  cupola  acts  as  a 
chimney,  although  the  two  or  more  cupolas  necessary  in  a  foundry 
may  lead  into  a  common  chimney. 

Under  the  base  ring  are  hinged  two  iron  doors,  FF,  held  up  by 
an  iron  prop  when  the  cupola  is  in  use.  About  12  inches  above  the 
sand  bed  is  the  slag  hole,  and  about  8  inches  further  up  are  the 
tuyere  holes.  The  tuyeres  are  merely  pieces  of  iron  pipe  extending 
through  the  cupola  shell  and  brick  lining.  The  tuyere  holes  are 
encircled  by  the  blast  or  wind  box  which  receives  ordinary  air  at  a 
low  pressure  from  a  blower  and  delivers  it  through  the  tuyeres  when 
the  cupola  is  in  operation.  The  blast  box  has  a  small  mica  peep 
door  opposite  each  tuyere  to  enable  the  melter  to  see  the  surface  of 
the  molten  iron.  The  cupola  is  charged  from  the  charging  platform 
through  the  charging  door  about  9  feet  above  the  bottom.  The 
lining  bricks  are  supported  at  intervals  by  angle  iron  lining-shelves 
as  shown. 

Cast  iron  melts  at  about  2200°  F.  If  the  cupola  blower  breaks 
down,  a  jet  of  steam  in  the  base  of  the  cupola  chimney  will  induce 
a  draft  sufficient  at  least  for  slow  melting. 

268.  Operation  of  the  Cupola. — A  cycle  of  service  for  a  cupola 
in  active  use  is  usually  repeated  each  24  hours.     Briefly  the  opera- 
tion throughout  the  24  hours  is  as  follows :     A  day's  melting  hav- 
ing been  finished,  and  the  blower  stopped,  all  metal  and  slag  are 
drained  out  at  the  tapping  hole.    The  prop  is  knocked  away,  and  the 
doors  FF  swing  down.     The  sand  bottom  and  any  unburnt  fuel 
drop  out. 

Next  morning  the  cupola  is  cool  and  the  melter  and  his  helper 
proceed  to  prepare  it  for  use.  Slag  is  chipped  from  the  lining, 
which  is  patched  where  needed  with  plastic  fire  clay.  Old  sand  is 
dug  from  the  doors,  breast  and  tapping  spout.  The  doors  are  then 
propped  up  and  the  melter  goes  down  through  the  charging  door  to 
prepare  a  new  bottom.  This  is  made  about  4  inches  thick,  and  con- 


248  MECHANICAL  PROCESSES 

sists  of  a  thin  layer  of  cinder,  a  layer  of  new  moulding  sand  and  a 
coating  of  thick  clay  wash.  The  sand  bottom  continues  out  to  the 
end  of  the  tapping  spout. 

After  the  bottom  has  dried  about  an  hour,  a  wood  fire  is  built  in 
the  cupola.  The  breast  is  rammed  with  new  sand  around  an  iron 
pipe,  and  the  pipe  is  then  withdrawn  to  form  the  tapping  hole.  • 

Coke  and  iron  are  weighed  out  for  the  charge  and  are  hoisted  to 
the  charging  platform.  A  hot  coke  fire  is  gradually  built  up,  the 
blower  is  started,  and  the  charging  begins.  The  charge  consists  of 
alternate  layers  of  coke  and-  iro^  and  each  layer  must  be  weighed 
to  make  the  operation  of  the  cupola  uniform  and  to  insure  enough 
coke  to  melt  the  iron.  Pig  and  scrap  iron  are  charged  together. 
Molten  metal  appears  at  the  tapping  hole  about  half  an  hour  after 
iron  is  charged,  and  this  hole  is  stopped  with  a  clay  plug  jammed 
into  place  on  the  end  of  a  heavy  round  stick. 

In  the  meantime,  the  f  oundrymen  are  -assembling  the  ladles  to  be 
used  in  pouring  the  moulds.  A  wood  fire  is  built  in  each  ladle  to 
keep  it  from  chilling  the  molten  metal  it  receives.  When  enough 
molten  metal  accumulates  in  the  cupola,  the  clay  plug  is  dug  out 
with, an  iron  bar,  ladles  are  filled,  and  the  tapping  hole  is  again 
stopped. 

Charging  continues  from  the  upper  platform  so  long  as  metal 
is  needed,  and  when  all  moulds  are  poured,  the  remaining  iron  is 
run  from  the  cupola  and  the  blower  is  stopped. 

269.  Ladles. — Iron  is  received  in  ladles  from  the  cupola  and  is 
poured  from  these  into  moulds.  Ladles  are  made  of  rolled  steel 
plate  and  plastered  inside  with  a  wet  mixture  of  silica  sand  and  fire 
clay.  Large  ladles  are  lined  with  fire-clay  bricks,  plastered  over 
with  clay.  Small  ladles  are  carried  in  ladle  shanks  by  one  or  more 
men,  and  large  ladles  must  be  carried  by  the  crane.  A  "  bull 
shank"  is  shown  in  Fig.  31.  Before  receiving  molten  metal,  ladles 
must  be  thoroughly  dry. 

Metal  for  a  very  large  casting  must  be  gradually  assembled  in 
several  large  ladles  until  there  is  enough  to  fill  the  mould.  After 
it  is  tapped  very  hot  into  the  ladles,  it  is  kept  hot  by  a  charcoal  fire  on 
the  surface  of  the  metal. 

All  ladles  and  crucibles  must  be  skimmed 'at  the  pouring  spout 


THE  FOUNDRY 


249 


with  an  iron  bar  while  pouring.  Very  hot  metal  makes  a  good  im- 
pression in  the  mould,  but  is  very  searching,  requires  more  venting 
of  the  mould,  and  shrinks  more  than  a  metal  not  so  hot. 


FIG.  133. — Foundry  Cupola. 

270.  Foundry  Iron. — Although  foundry  iron  is  now  selected  by 
its  composition  as  shown  by  chemical  analysis,  yet  the  designations 
of  white,  mottled,  and  grey  irons,  are  still  used  to  classify  pig  iron 
.according  to  the  carbon  it  contains.  White  iron,  with  no  uncom- 


250 


MECHANICAL  PROCESSES 


bined  carbon,  is  too  hard  for  castings  which  must  be  machined. 
Grey  iron,  with  much  uncombined  carbon,  is  easiest  to  melt  and 
easiest  to  cut.  A  mottled  iron  is  strong,  tough  and  not  difficult  to 
machine. 

Cast  iron  containing  much  free  carbon  expands  upon  cooling., 
due  to  separating  out  of  graphite  from  solution.  This  is  an  ad- 
vantage in  casting,  as  it  balances  the  contraction  due  to  cooling. 

Scrap  iron  must  not  be  used  in  high-grade  castings  unless  it 
comes  from  similar  castings. 


L/c/ 


FIG.  134. — Brass  Melting  Furnace. 

271,  Brass  Furnaces. — The  materials  and  methods  used  in  mak- 
ing iron  and  brass  moulds  are  practically  the  same,  although  the 
means  of  melting  these  metals  for  castings  are  different  because 
brass  melts  at  a  lower  temperature  (brass  about  1700°  F.,  copper 
about  2000°  F.)  than  does  iron. 

Fig.  134  shows  a  typical  crucible  furnace  for  melting  brass.  It 
is  shown  as  arranged  for  oil  fuel,  but  may  be  used  for  hard  coal 
or  coke  by  removing  the  oil  burner,  stopping  up  the  burner  hole  D 
and  removing  the  bricks  K  from  the  grate  bars. 


THE  FOUNDKY 


There  are  patented  forms  of  oil  furnaces  which  are  self-contained 
and  may  be  set  at  any  place  desired  about  the  foundry  floor. 

A  reverberatory  furnace  is  used  to  melt  brass  for  a  large  casting, 
but  if  this  is  not  installed,,  a  large  casting  can  be  made  by  assem- 
bling in  a  large  ladle  the  molten  metal  from  several  crucibles. 

In  Fig.  134,  the  furnace  is  built  of  brick  in  a  concrete-lined  pit. 
The  melting  space  H  is  enclosed  by  fire-brick  walls  and  covered  by  a 
movable  lid.  A  furnace  is  composed  of  a  number  of  these  melting 
spaces  in  a  row. 

The  burner  forces  oil  and  air  through  the  opening  D  into  a  flame 
which  strikes  the  corner  of  the  base  B  and  surrounds  the  crucible  C. 
The  chimney  conduit  G  conducts  gases  of  combustion  to  a  tall 
chimney. 

Two  bricks  on  edge,  or  better,  a  bed  of  glowing  hard 
coal  must  hold  the  crucible  off  the  grate  bars  when 
coal  or  coke  heating  is  done,  otherwise  its  bottom 
would  be  too  much  cooled  from  the  air  through  the 
bars  to  allow  melting  of  the  contents.  The  ash  pit  A 
is  large  enough  to  afford  a  good  draft  for  coke  or  coal. 

Brass  is  alloyed  by  melting  the  required  amount 
of  copper  and  then  stirring  in  the  zinc  in  small  pieces 
with  an  iron  rod.  Salt,  sal  ammoniac,  or  charcoal 
may  be  used  as  a  flux  to  avoid  oxidation  of  the  sur- 
face of  the  molten  metal.  Scrap  brass  must  not  be 
used  in  high-grade  castings  unless  its  composition  is 
known  to  be  the  same  as  that  intended  for  the  cast- 
ings. Even  then,  a  careful  fluxing  is  required  to 
remove  any  possible  oxidized  metal  contained  in  the 
scrap. 

Fig.  135  shows  a  pair  of  tongs  for  lifting  crucibles  from  brass 
or  crucible-steel  furnaces.  A  tackle  hooked  to  the  eyebolt  B  lifts 
the  crucible  and  lowers  it  into  a  ladle  shank.  The  mould  is  poured 
from  the  crucible. 

272.  Defects  in  Castings. — The  following  defects  and  their  causes 
are  well  known  to  foundry  men : 

(1)  Surface  and  interior  cavities  are  caused  by  too  little  metal, 
or  by  runners  and  risers  too  small  to  remain  liquid  and  feed  the 
casting  until  it  has  "  set "  throughout  its  mass. 


FIG.  135. 

Crucible 

Tongs. 


252  MECHANICAL  PROCESSES 

(2)  Cold  shuts   are   caused   by   drilled   metal.     When   poured, 
sluggish  metal  becomes  so  chilled  that  it  does  not  unite  when  it 
meets  from  opposite  sides  of  the  mould. 

(3)  Blow  holes  are  caused  by  air,  gas,  or  steam  under  the  sur- 
face of  the  casting  when  it  solidifies.     Blow  holes  are  from  air 
entrained  in  a  partially  filled  runner,  from  air  entrapped  in  the 
mould  space  and  from  steam  forced  into  the  mould  from  the  sand 
due  to  improper  venting  and  drying.    If  a  metal  is  very  fluid  when 
poured,  air  and  gases  will  rise  to  the  surface  and  escape.    The  metal 
itself  contains  little  or  no  gas  before  pouring. 

(4)  Sand  holes  and  cuts  are  formed  by  loose  sand  in  the  mould. 
Sand  from  the  mould  surfaces  may  come  off  in  patches  known  as 
"  scabs  "  due  to  poor  venting.     If  the  patch  of  sand  breaks  up,  it 
forms  sand  holes,  but  if  it  remains  intact,  metal  encloses  it  and 
forms  a  cut.    Sand  will  float  if  the  metal  is  sufficiently  fluid. 

(5)  Shrinkage  cracks  are  caused  by  a  mould  or  core  too  rigid  to 
allow  a  casting  to  shrink  without  cracking. 

(6)  Strains  and  warps  are  caused  by  uneven  cooling.     A  strain 
is  not  visible,  but  may  cause  the  casting  to  crack  if  hammered.     A 
warp  distorts  the  shape  of  the  casting. 

(7)  Sponginess  is  caused  by  impurities  in  the  metal  when  poured. 
It  generally  shows  in  brass  or  bronze  castings  when  tested  under 
hydrostatic  pressure  and  is  caused  by  porous  oxidized  metal  in  the 
casting.     The  defect  is  revealed  by  a  sweating  of  the  casting  under 
high  pressure.    Globules  of  water  seep  through  more  or  less  rapidly 
and  trickle  from  the  surface. 

(8)  Castings  may  be  of  poor  material,  too  hard  for  machining, 
or  defective  in  strength.     These  defects  are  avoided  by  an  analysis 
of  the  material  before  casting. 

273.  Remedies  for  Defective  Castings. — In  some  cases  defective 
castings  may  be  remedied. 

(1)  Strains  are  removed  from  castings  by  annealing.     This  is 
usually   necessary   only   with   steel   castings,    or   chilled    cast-iron 
castings. 

(2)  A  warped  casting  may  be  straightened  by  weighting  it  and 
building  a  charcoal  fire  under  it  to  heat  it  red  hot.    Provision  must 
be  made  not  to  let  the  weight  bend  the  casting  more  than  is  needed. 


THE  FOUNDRY  253 

(3)  A  small  hole  caused  by  sponginess  may  be  drilled  out  and 
plugged.     A  small  blow  hole  or  small  collection  of  blow  holes  may 
frequently  be  remedied  in  the  same  way. 

(4)  Cracked  or  broken  castings  may  in  many  cases  be  repaired 
by  "  burning  on/?  by  electric  welding.,  or  brazing. 

The  Steel  Foundry. 

274.  Steel  Castings. — In  strength  and  other  qualities  steel  cast- 
ings resemble  steel  forgings  much  more  than  they  do  cast-iron  cast- 
ings.    But  for  their   marked   superiority  over   cast-iron   castings 
doubtless  their  greater  cost  would  have  stopped  their  production. 
Properly  made  steel  castings  are  not  brittle,  but  will  stand  a  re- 
markable degree  of  cold  bending  without  showing  cracks  or  flaws. 
They  are  much  stronger  than  wrought-iron  forgings,  and  approach, 
or  in  many  qualities  equal  or  exceed,  the  elastic  and  tensile  strength 
of  rolled  or  forged  steel.     They  are  cheaper  than  forgings,  except 
possibly  those  forgings  made  by  the  drop-forging  process.     Cast- 
steel  castings  are  usually  low  enough  in  carbon  to  stand  welding. 

In  considering  the  strength  of  steel  castings,  the  elastic  strength 
is  highly  important,  as  a  casting  is  practically  ruined  after  its 
elastic  strength  has  been  exceeded.  A  high  per  cent  of  elongation 
and  high  elastic  limit  are  desirable.  Absence  of  these  is  an  indi- 
cation of  brittleness. 

275.  Steel  and  Iron  Foundries  Compared. — Although  the  work  of 
making  steel  castings  is  closely  associated  with  the  steps  in  making 
cast-iron  castings,  yet  there  are  several  requirements  of  great  im- 
portance in  the  preparation  of  steel  moulds  which  mark  the  produc- 
tion of  steel  castings  as  an  art  by  itself. 

The  steel  foundry  is  generally  an  independent  branch  of  industry 
just  as  are  many  branches  for  the  re-manufacture  of  metals. 

Comparing  the  steel  and  the  iron  foundry,  their  locations  are  alike 
in  requirements,  equipment  and  interior  arrangement  are  very 
similar,  moulds  must  embody  the  same  essentials,  the  same  re- 
quirements hold  for  sand  used  in  moulding,  and  the  tools,  acces- 
sories, and  most  of  the  minor  moulding  materials  are  the  same. 

The  differences  between  the  requirements  of  moulds  for  making 
cast-iron  and  steel  castings  are  differences  in  degree  rather  than 
17 


254  MECHANICAL  PROCESSES 

differences  in  kind.  These  differences  are  due  (1)  to  the  effects  of 
higher  heat  of  molten  steel  when  poured  into  the  mould,  and  (2) 
to  its  greater  shrinkage  in  cooling,  for  it  does  not  expand  as  does 
cast  iron,  which  precipitates  some  of  its  carbon. 

The  shrinkage  of  steel  is  about  twice  that  of  cast  iron. 

276.  Moulds  for  Steel  Castings. — Dry  sand  moulds  made  in  iron 
flasks  are  used  for  steel  castings,  although  small  steel  castings  are 
frequently  made  in  green  sand  moulds  contained  in  wood  flasks. 
The  boundry  between  the  use  of  green  and  dry  sand  moulds  in  this 
work  depends  upon  the  care  and  skill  of  the  moulder,  but  castings 
of  over  a  few  pounds  are  safest  and  soundest  when  made  in  dry 
sand.    A  dried  mould  must  be  dried  thoroughly  to  prevent  damage 
from  steam,  and  it  is  the  practice  of  some  steel  foundries  to  heat 
green  sand  moulds  gently  over  night  in  a  drying  room. 

277.  Particular  Requirements  of  Steel  Moulds. — The  higher  heat 
of  steel  when  cast  requires  that  (1)  particular  attention  be  paid  to 
the  venting  of  moulds,  and  that  (2)  the  mould  surfaces  be  especially 
treated  to  prevent  washing  away,  or  "  scabbing/'  when  metal  is 
poured  into  them,  and  to  prevent  fusing  in  contact  with  the  highly 
heated  metal.    The  greater  shrinkage  of  cast  steel  requires  (1)  that 
large  feeding  heads  be  attached  to  the  heavy  parts  of  a  casting  to 
prevent  shrinkage  cavities  in  the  casting,  and   (2)  that  cores  and 
moulds  be  composed  of  materials  which  will  crush  readily  or  which 
can  be  dug  out  to  avoid  shrinkage  cracks. 

Steel  moulds  are  rammed  up  harder  than  iron  or  brass  moulds. 

278.  Surfaces  of  Steel  Moulds. — After  the  pattern  has  been  re- 
moved from  a  steel  mould,  the  face  of  the  mould  and  particularly 
any  sand  projections  subject  to  the  wash  of  the  metal,  are  stuck 
with  wire  nails  more  or  less  close  together.    The  heads  of  these  nails 
are  often  visible  in  the  face  of  the  mould,  and  their  imprints  may 
be  seen  on  the  surfaces  of  many  steel  castings. 

The  surface  of  the  mould  is  sprinkled  with  molasses  water  or 
similar  sticky  preparation  to  make  the  sand  hold  together  better, 
and  a  powder  or  wash  of  ground  quartz  or  other  pure  silica  is 
dusted  or  brushed  over  the  entire  mould  surface  and  over  the  part- 
ing adjacent  to  the  mould  cavity,  to  make  these  surfaces  highly 
refractory.  The  molasses  water  also  aids  to  hold  this  silica  facing, 
as  the  facing  is  not  adhesive  itself. 


THE  FOUNDRY  255 

279.  Means  of  Avoiding  Shrinkage  Cracks. — Shrinkage  cracks 
may  occur  where  thin  and  thick  parts  of  a  casting  join,  due  to  the 
unequal  rate  of  cooling  of  the  different  masses  of  metal.  These  are 
prevented  by  making  changes  of  thickness  very  gradual,  even  at  the 
expense  of  making  the  casting  heavier  and  necessitating  machining 
away  later  of  some  of  the  extra  metal. 

A  very  common  practice  to  prevent  shrinkage  cracks  where  two 
surfaces  meet  at  an  angle,  is  shown  in  Fig.  136.  The  sides  c  and  d 
cool  quicker  than  the  larger  mass  of  metal  at  the  corner,  and  in 
cooling  they  tend  to  shrink  away  from  it  and  to  cause  a  fracture 
in  the  hotter  and  weaker  metal  there.  To  prevent  fracture,  the 
moulder  cuts  thin  webs  or  gussets  I,  about  4  or  5  inches  apart,  in 
the  mould.  These  webs  cool  first,  keeping  the  sides  together  at  the 
corner  while  the  metal  mass  of  the  corner  is  cooling.  These  webs 


cause  an  internal  strain  by  their  cooling,  but  this  is  relieved  by 
annealing  the  casting,  and  the  webs  are  then  cut,  away,  leaving  a 
fillet  as  at  a. 

280.  Avoiding  Surface  or  Interior  Cavities. — The  great  shrinkage 
of  steel  would  cause  surface  or  interior  cavities  in  the  casting  were 
it  not  fed  by  its  runners,  risers,  and  feeding  heads.  The  static 
pressure  of  the  metal  in  these  injures  the  filling  of  the  mould  pro- 
vided they  are  large  enough  in  diameter  to  remain  liquid  until  the 
casting  has  solidified.  A  feeding  head  is  merely  an  extra  riser  over 
a  heavy  part  of  the  casting,  and  the  fluidity  of  both  feeding  heads 
and  risers  is  prolonged  by  churning  the  metal  in  them  with  small 
iron  rods.  Often  a  riser  or  feeding  head  is  %  or  %  the  weight  of 
the  casting,  and  is  as  much  as  ten  inches  in  diameter  for  large 
castings. 

The  removal  of  large  risers,  runners  and  feeding  heads  requires 
considerable  work,  and  adds  much  to  the  expense  of  steel  castings. 


256  MECHANICAL  PROCESSES 

An  old  and  effective  method  is  to  saw  them  off  with  a  cold  steel  saw, 
but  where  a  shop  has  facilities  for  electric  cutting,  a  much  cheaper 
way  is  to  cut  them  off  by  use  of  the  electric  arc.  One  electrode  is 
fastened  to  the  riser  and  the  other,  suitably  rigged  to  be  handled 
by  a  workman,  is  passed  around  the  riser  neck  close  to  the  casting. 
The  intense  heat  of  contact  melts  a  groove  around  the  riser,  reducing 
its  diameter  until  it  can  be  knocked  off  by  a  sledge.  The  brilliancy 
of  the  arc  is  such  that  the  workman  must  wear  a  metal  head  shield 
provided  with  black  glass  sight  openings,  and  the  work  is  done 
within  an  enclosure  to  keep  others  from  looking  at  the  arc. 

Another  method  lately  developed  for  such  cutting  is  the  oxy- 
acetylene  burner. 

281.  Steel  for  Castings. — In  steel  works,  where  steel  is  made, 
castings  are  poured  from  open-hearth,  Bessemer,  or  crucible  steel,  as 
may  be  required.  The  making  of  steel  castings  in  large  steel  works 
is  usually  an  incidential  operation,  as  steel  is  made  principally  for 
rolling  into  various  shapes,  as  described  in  Chapter  Y. 

In  steel  foundries,  where  steel  is  made  only  for  castings,  a  small 
converter  is  used  to  make  steel  by  "  blowing "  pig  iron  melted  in 
the  foundry  cupolas.  This  is  essentially  the  Bessemer  process.  The 
steel-making  equipment  of  the  usual  steel  foundry  consists  of  (1) 
two  or  more  cupolas  for  melting  cast  iron,  (2)  one  or  more  small 
converters  (usually  in  America  the  Tropenas  type  of  about  two 
tons  capacity),  and  (3)  a  small  cupola  for  melting  the  ferro-man- 
ganese  or  other  recarburizer  which  is  mixed  with  the  converter  con- 
tents after  blowing. 

In  quality,  steel  for  castings  must  be  low  in  phosphorus  and  sul- 
phur, although  these  ingredients  are  not  so  objectionable  in  cast  as 
in  rolled  steel.  Silicon  and  manganese  should  be  kept  within  limits, 
and  particularly  should  iron  oxide  and  dissolved  gas  be  reduced  to 
the  lowest  limits  possible.  The  hardness  of  the  casting,  and  directly 
its  tensile  strength  and  brittleness,  depend  upon  the  per  cent  of 
carbon  contained.  Hard  castings  contain  up  to  .9%  of  carbon, 
medium  castings  contain  around  .5%,  and  soft  castings  contain 
around  .3%.  Most  castings  contain  between  .35%  and  .50%.  Soft 
castings  are  hardest  to  obtain  because  of  the  higher  melting  point 
of  low-carbon  steel.  This  grade  of  castings  often  looks  very  rough. 
The  very  best  steel  castings  contain  about  2>y2%  of  nickel. 


THE  FOUNDRY  257 

282.  The  Tropenas  Converter. — The  product  of  this  converter  is 
acid  steel  produced  as  in  the  Bessemer  process  except  that  the 
Tropenas  converter  directs  its  blast  against  the  surface  and  not 
through  the  metal.  Fig.  137  shows  a  Tropenas  converter  in  cross- 
section.  The  lining  is  the  same  as  that  for  an  acid  Bessemer  con- 
verter, and  the  tuyeres,  arranged  in  two  horizontal  rows  in  the  side 
of  the  converter,  are  formed  of  lining-bricks  with  holes  through 
them.  The  lower  tuyeres,  used  throughout  the  blow,  are  called  the 
reaction  tuyeres  and  they  open  into  the  main  wind  box  (7.  The 
upper  tuyeres,  used  during  the  latter  part  of  the  blow,  are  called  the 
combustion  tuyeres,  and  open  into  the  auxiliary  wind  box  D.  The 
advantages  claimed  for  this  converter  are  (1)  the  blast  pressure  is 


PIG.  137. — Converter  for  Steel  Foundries. 

very  low  (not  over  5  Ibs.)  as  it  is  not  forced  through  the  metal,  and 
therefore  requires  a  less  powerful  blower;  (2)  the  surface  impact 
agitates  the  metal  less,  causing  it  to  take  up  less  gas  than  the 
through  blow ;  and  ( 3 )  the  combustible  impurities  in  the  metal  are 
more  completely  burned. 

The  converter  is  charged  with  very  hot  metal  from  the  cupola,  the 
blast  is  admitted  through  the  lower  tuyeres,  and  the  burning  out  of 
the  impurities  proceeds  as  in  the  acid  Bessemer  process.  As  the 
blast  enters  through  the  tuyeres,  it  strikes  the  surface  of  the  metal 
at  an  angle,  agitating  it  slightly,  and  when  the  flame  from  the 
mouth  of  the  converter  begins  to  die  down,  air  is  admitted  through 
the  upper  tuyeres  for  a  greater  supply  and  better  distribution  of 
oxygen.  The  blow  lasts  but  a  few  minutes,  and  when  the  flame  dies 


258  MECHANICAL  PROCESSES 

out,  the  recarburizer  is  poured  in  and  stirred.     The  steel  is  then 
poured  into  ladles  and  taken  to  the  moulds. 

283.  Temperature  of  Steel  for  Pouring. — The  temperature  of 
steel  when  poured  into  moulds  is  highly  important,  and  varies  with 
the  size  of  the  casting.     An  experienced  foundry  superintendent 
judges  the  right  pouring  temperature  by  simple  inspection.    Hotter 
metal  is  needed  for  small  intricate  castings  than  for  large  and 
massive  castings. 

If  metal  is  too  hot,  it  is  very  searching,  and  causes  piping  or 
cavities,  and  possibly  shrinkage  cracks,  by  excessive  and  unequal 
contraction  in  the  mould.  If  below  a  certain  fluidity,  the  mould 
may  not  fill  completely  or  cold  shuts  may  be  formed.  Small  bits  of 
aluminum  thrown  into  the  ladle  reduce  iron  oxide,  thus  helping  the 
fluidity  of  the  steel. 

After  pouring  steel  moulds,  they  are  watched  to  see  that  the 
mould  feeds  from  the  risers  and  feedings  heads,  and  when  the  metal 
has  "set,"  clamps  are  removed  from  the  flasks,  and  the  mould  is 
somewhat  loosened  to  allow  the  casting  free  contraction,  yet  the  cast- 
ing must  not  be  laid  bare  to  sudden  chilling. 

284.  Annealing    Steel    Castings. — Because    of   the    considerable 
change  in  form  by  contraction  during  cooling,  steel  castings  of  large 
bulk  and  particularly  varying  thickness,  are  apt  to  be  under  stress 
due  to  the  contraction  of  a  heavier  and  hotter  part  after  a  thinner 
part  has  cooled.    Especially  is  this  the  case  with  castings  naturally 
brittle  from  a  high  per  cent  of  carbon.    The  stresses  are  removed, 
or  at  least  are  reduced  within  safe  limits,  by  annealing. 

This  may  be  done  in  any  kind  of  a  brick  furnace  which  can  be 
evenly  heated  to  the  temperature  required.  After  the  heat  has  re- 
mained for  a  while  at  its  maximum,  the  furnace  openings  are 
stopped  with  bricks  or  clay  to  insure  slow  and  even  cooling  as  the 
fire  dies  out.  Castings  may  be  covered  with  sand  to  assist  in  the 
gradual  and  even  heating  and  cooling  of  light  and  heavy  parts. 
Castings  are  heated  red,  and  annealing  requires  from  60  to  180 
hours. 

The  elastic  and  tensile  strength  of  a  casting  is  controlled  to  such 
a  degree  by  annealing  that  many  investigators  are  seeking  to  find 
the  factors  controlling  this  process.  Method  of  heating,  time  and 


THE  FOUNDRY  259 

temperature,,  all  enter  into  the  problem.  Annealing  furnaces  need 
pyrometers  to  insure  best  results. 

By  exercising  care  in  allowing  small  and  medium-sized  castings 
to  cool  in  the  moulds,  the  necessity  of  annealing  may  be  avoided. 

285.  Defects  in  Steel  Castings. — Steel  castings  are  subject  in  gen- 
eral to  the  same  defects  named  for  cast-iron  castings,  but  particu- 
larly does  the  manufacturer  of  steel  castings  have  to  be  continually 
on  guard  against  three  classes  of  defects  named,  as  follows : 

(1)  Cavities  on  the  surface  or  hollows  in  the  body  of  the  casting 
(piping)  caused  by  runners,  risers  and  feeding  heads  too  small  to 
feed  the  casting  as  it  cools.    The  hollows  are  so  small  at  times  as  to 
resemble  blow  holes. 

(2)  Shrinkage  cracks  or  internal  strains  due  to  unequal  rates  of 
cooling  of  various  parts  or  resistance  of  the  mould  to  contraction 
of  the  metal. 

(3)  Blow  holes  or  small  globules  of  gas  or  air  enclosed  in  the 
metal.     They  may  be  due  to    (a)    poorly  vented  or  poorly  dried 
moulds  in  which  air  and  steam  do  not  escape  from  the  mould  cavity, 
or  (6)  to  carbon  monoxide  and  other  gases  dissolved  in  the  metal 
while  very  hot  in  the  converter  and  which  are  thrown  out  of  solu- 
tion as  the  metal  cools,  a  defect  greatly  remedied  by  the  chemical 
action  of  ferro-silicon  or  aluminum. 

One  test  usually  specified  to  determine  the  soundness  of  steel  cast- 
ings is  to  suspend  and  strike  them  with  a  hammer,  or  to  hammer 
without  suspending.  This  does  not  alwa}^s  show  the  defect  a  cast- 
ing may  have. 

Sometimes  a  cracked  casting  which  has  been  annealed  may  be 
made  good  by  welding  on  a  piece  to  repair  the  crack. 


CHAPTER  X. 
THE  BLACKSMITH  SHOP. 

286.  The  Blacksmith  and  Forge  Shop, — The  work  of  shaping 
iron  into  many  forms  by  heating  and  hammering  is  a  process 
which  has  been  long  in  vogue,  and  it  is  far  more  widely  known  and 
practiced  to-day  than  any  of  the  other  metal-shaping  processes. 
Every  village,  and  every  farming  and  mining  community  has  its 
blacksmith  shop.  The  simple  equipment  needed  for  blacksmith 
work  of  the  cruder  sort  makes  this  process  readily  available  at  any 
place  where  heat,  hammer,  and  improvised  anvil  are  at  hand. 

Blacksmithing  is,  strictly  speaking,  a  re-manufacturing  process, 
and  it  is  practiced  independent  of  other  shops  in  turning  out  ready 
for  use  many  products  of  forged  iron  with  which  everyone  is 
familiar. 

In  a  large  building  and  repairing  establishment  the  work  of  mak- 
ing forgings  is  divided  between  (1)  the  blacksmith  shop,  where 
forgings  are  made  by  manual  labor  on  the  anvil  as  in  the  village 
shop,  and  (2)  the  forge  shop,  where  large  forgings  are  made  by  the 
steam  hammer. 

The  forgings  made  in  the  blacksmith  shop  are  for  the  most  part 
used  just  as  the  shop  turns  them  out,  or  else  they  may  require  no 
other  finishing  than  a  little  filing  or  grinding.  Large  forgings 
made  under  the  steam  hammer  are  almost  always  rough  shapes  to 
be  machined  accurately  to  required  dimensions  in  the  machine  shop. 
Examples  of  this  class  of  large  forgings  are  crank  and  line  shafts, 
cross-heads,  connecting  and  piston  rods,  large  braces  and  bolts,  used 
in  marine  and  stationary  engines.  Many  parts  of  engines  subject 
to  stresses  in  motion  are  made  of  large  forgings  because  of  the 
greater  homogeneity  and  reliability  of  their  material  as  compared 
with  cast  steel. 

The  largest  class  of  forgings,  as  large  gun  parts,  shafts  of  large 
engines,  etc.,  are  special  products  in  size  and  quality  of  material, 
and  these  are  made,  as  was  outlined  in  Chapter  V,  by  the  steel 
works  which  produce  the  special  ingots  necessary  for  them. 


THE  BLACKSMITH  SHOP  261 

The  process  of  drop-hammer  forging  has  narrowed  the  field  of 
work  for  the  blacksmith  shop,  and  not  only  has  the  drop  hammer 
succeeded  in  making  many  forgings  formerly  made  on  the  anvil 
by  hand,  but  it  makes  many  superior  and  complicated  forged  shapes 
heretofore  made  only  as  iron  or  steel  castings  or  cut  to  shape  at 
great  expense  in  the  machine  shop. 

287.  Materials  for  Forcings. — The  stock  for  working  into  small 
forgings  comes  from  the  rolling  mill  as  rods  and  bars  of  various 
sections.     This  material,  at  the  present  day,  is  principally  mild 
steel,  this  having  displaced  most  of  the  wrought  iron  used  before 
the   days   of  mild   steel.      However,   many   blacksmiths   use    only 
wrought  iron  in  work  which  must  be  welded,  as  this  material  has 
the  quality  of  becoming  very  plastic  at  a  high  heat  before  melting. 
High-carbon  steel  and  cast  iron  cannot  be  welded  on  the  anvil  be- 
cause the  carbon  in  them  begins  to  burn  out  before  welding  heat  is 
reached,  and  because  the  melting  point  is  not  preceded  by  a  helpful 
condition  of  plasticity. 

Oftentimes  for  special  work  in  marine  use,  the  stock  of  the  black- 
smith shop  includes  rods  and  bars  of  certain  bronzes  which  can  be 
forged  and  welded  as  can  iron. 

A  shop  always  carries  in  stock  some  bars  of  high-carbon  or  alloy- 
crucible  steel  for  making  metal-cutting  tools.  . 

For  steam-hammer  forgings,  billets  and  blooms,  of  designated 
dimensions  and  quality,  are  ordered  from  the  rolling  mills.  These 
are  usually  of  mild  steel,  but  may  be  of  wrought  iron.  For  high- 
grade  forgings,  nickel  steel  is  much  used. 

Steel  castings  are  occasionally  heated  and  shaped  differently  from 
the  shapes  given  by  the  mould,,  though  this  adds  much  to  their 
cost  and  they  should  be  annealed  afterward. 

288.  Shop  Equipment  for  Hand  Forging. — This  equipment  con- 
sists of  (1)  a  suitable  forge  for  heating,  (2)  an  anvil  mounted  solidly 
at  a  convenient  working  height,  (3)  hammers  in  form  and  weight 
suitable  for  shaping  forgings  to  best  advantage,  and  (4)  appliances 
to  hold  and  to  assist  in  shaping  material  worked  upon.    Also,  there 
is  always  more  or  less  accessory  equipment  in  the  blacksmith  shop, 
such  as  vise  and  bench,  cold  chisels,  files,  grindstone,  taps  and  dies, 
hand-power  drill,  and  other  appliances  from  machine-shop  equip- 
ment, employed  for  cold  iron  work. 


262  MECHANICAL  PROCESSES 

289.  The  Forge. — Forges  are  of  various  forms,  portable  and  sta- 
tionary, and  framed  of  brick  or  iron.  Most  of  them  use  coal  for 
fuel,  but  brick-lined  furnaces  for  oil  or  gas  fuel  are  now  in  common 
use.  For  coal-burning  furnaces,  the  essential  parts  are  (1)  the 
forge-pan  or  hearth,  into  which  leads  a  tuyere  from  underneath 
for  conveying  air  to  the  under  side  of  the  fire,  (2)  the  chimney,  or 
exhaust  hood  and  duct  for  conveying  away  smoke,  and  (3)  the 
bellows  or  blower  for  forcing  air  through  conduits  to  the  tuyere. 

The  oil  or  gas-burning  forge  is  a  brick-lined  box  open  at  the  top 
or  on  one  side  for  putting  in  work  to  be  heated.  It  is  provided  with 
a  burner  which  blows  air  and  fuel  into  the  enclosed  space  where  it 
burns  in  a  continuous  flame.  The  products  of  combustion  usually 
escape  into  the  surrounding  atmosphere. 


FIG.  138. — Anvil. 

Attached  to  or  beside  a  forge  is  an  iron  or  wood  quenching  basin 
filled  with  water,  and  racks  for  holding  tools  which  the  smith  uses 
in  forging.  A  small  iron  poker  and  hooked  scraper  are  essential 
fire  tools. 

290.  The  Anvil. — Fig.  138  shows  an  anvil  of  usual  form.  The 
body  and  horn  are  made  of  wrought  iron  or  forged  mild  steel,  with 
a  %-inch  face  of  crucible  tool  steel  welded  on  the  body.  However, 
some  anvils  are  made  by  casting  upon  a  tool-steel  face  and  horn  a 
body  of  a  gun-metal  grade  of  cast  iron.  The  face  and  horn  are  cast 
to  shape  from  crucible  steel,  and  are  then  placed  to  form  the  bottom 
of  a  mould.  They  are  heated  to  a  red  heat  when  the  mould  is  poured 
to  insure  complete  welding  of  the  two  metals.  After  the  tool-steel 
face  is  welded  on,  it  is  hardened  by  heating  and  quenching  in  water 
and  then  ground  to  a  working  surface. 


THE  BLACKSMITH  SHOP  263 

When  a  hole  is  to  be  punched  in  a  forging,  it  is  done  over  the 
round  hole  of  the  anvil.  The  square  hole  is  for  receiving  the  stems 
of  anvil  tools. 


FIG.  139. — Hand  Hammer.  PIG.  140. — Sledge  Hammer. 

291.  Smiths'  Hammers. — These  are  made  of  a  medium-carbon 
crucible  cast  steel.  They  must  be  hard  though  not  brittle.  Hand 
hammers  weigh  about  two  pounds,  and  sledge  hammers  weigh 
from  5  to  20  pounds,  though  for  ordinary  work  about  10  pounds. 

Fig.  139  shows  a  hand  hammer  with  a  cross  pene  shape  of  small 
end.  Fig.  140  shows  a  sledge  with  a  straight  pene  shape  of  small 
end. 


Straight  Lipped  Tongs. 


Single  Pick  Up  Tongs. 


"  Gad  "  Tongs. 
FIG.  141.— Tongs. 

292.  Tongs  and  Anvil  Tools. — Fig.  141  shows  three  varieties  of 
tongs  much  used  in  blacksmithing,  though  there  are  many  special 
forms  for  holding  peculiarly  shaped  forgings. 


264 


MECHANICAL  PROCESSES 


Fig.  142  shows  tools  used  in  anvil  work, 
follows : 


They  are  designated  as 


(1)  Top  and  "bottom  swages,  for  rounding. 

(2)  Top  and  bottom  fullers,  for  necking. 

(3)  Hardie,  for  cutting  off. 

(4)  Flatter,  for  smoothing. 

(5)  Hot  chisel  (thin  edge),  for  cutting  hot  iron. 

(6)  Cold  chisel  (thick  edge),  for  cutting  cold  iron. 


PIG.  142. — Anvil  Tools. 

(7)   Round  punch,  for  punching  holes  in  hot  iron. 

(3)   Heading  tool,  for  forming  a  bolt  head. 

The  stems  of  the  bottom  swage,  bottom  fuller,  and  the  hardie, 
fit  in  the  square  hole  in  the  anvil.  The  heading  tool  has  a  metal 
handle,  and  the  remaining  tools  in  the  figure  have  hickory  handles. 

Fig.  143  shows  a  swage  block,  a  very  useful  adjunct  to  the  anvil 
in  shaping  and  bending  bars  of  any  shape. 

Many  sizes  of  the  tools  shown  and  many  tools  for  special  work, 
as  chain  making,  are  not  uncommonly  seen  in  a  well-equipped  shop. 


THE  BLACKSMITH  SHOP  265 

Anvil  tools  are  made  of  a  tough  grade  of  medium-carbon  crucible 
cast  steel.,  and  they  should  be  harder  than  forgings. 

293.  Fuel  for  Use  in  Forges. — Up  to  recent  years  soft  coal  was 
the  most  extensively  used  fuel  for  forges,  but  petroleum  residue  is 
now  much  used,  and  natural  gas  is  used  in  localities  which  supply  it. 

Soft  coal  is  used  because  its  gaseous  constituents  distil  off  con- 
tinuously during  burning  and  assist  the  solid  carbon  to  maintain 
a  steady  fire.  The  coal  used  must  be  of  a  quality  containing  very 
little  if  any  sulphur,  and  almost  free  from  mineral  matter  which 
will  not  burn  or  which  will  form  a  pasty  mass  of  slag  or  clinker  in 
the  fire.  It  should  be  a  free  coking  coal,  broken  into  small  lumps 


FIG.  143. — Swage  Block. 

which  will  stick  together  slightly  during  burning.  The  air  blast  is 
supplied  in  a  forge  to  increase  the  rapidity  of  combustion  in  one 
spot,  and  thus  supply  a  concentrated  quantity  of  heat  for  needs  of 
local  heating. 

Oil  used  in  forges  is  the  same  as  supplied  for  steam  boiler  uses, 
although  the  grades  low  in  sulphur  are  preferable.  To  attempt  the 
used  of  undistilled,  or  crude,  petroleum  would  be  dangerous  because 
of  the  gasolene  and  other  highly  volatile  constituents. 

294.  Heating  in  a  Forge. — A  clean  fire  of  incandescent  coal  all 
around  a  piece  to  be  forged  will  insure  even  heating.  There  must  be 
a  substantial  layer  of  burning  coal  between  the  forging  and  the 
tuyere,  else  the  oxygen  of  the  air  entering  through  the  tuyere  will 
burn  the  forging.  Also  the  supply  of  air  must  be  regulated  by  the 


266  MECHANICAL  PROCESSES 

damper  to  avoid  letting  more  in  than  can  be  consumed  by  the  burn- 
ing fuel,  as  any  excess  will  be  taken  up  by  the  hot  iron,  forming  a 
scale  of  iron  oxide  over  the  surface. 

The  simple  means  of  regulating  the  air  and  oil,  or  air  and  gas 
supply  to  oil  and  gas  furnaces  by  merely  turning  the  controlling 
valve  of  each,  makes  these  forges  superior  to  coal  forges. 

The  degree  of  heat  to  which  a  forging  should  be  raised  varies 
somewhat  for  different  kinds  of  work.  Welding  requires  a  high 
heat  to  bring  the  parts  to  be  joined  near  the  fusing  temperature,  but 
for  shaping  it  is  sufficient  to  bring  the  piece  to  a  red  heat.  A  large 
forging  should  be  heated  as  bright  as  can  be  without  burning  and 
it  is  often  heated  yellow  because  fewer  heats  are  necessary  and  the 
more  plastic  condition  at  high  heat  insures  the  hammer  impact 
reaching  further  into  the  mass  of  metal.  The  finishing  of  work  at  a 
low  red  heat  shapes  the  surface,  and  the  blows  then  should  not  be 
heavy.  No  forging  should  be  done  below  a  red  heat,  except  that 
light  blows  may  be  given  to  smooth  the  surface. 

The  heating  of  forgings  is  a  p.art  of  the  subject  of  the  heat  treat- 
ment of  steel,  which  is  now  a  matter  of  careful  study  among  those 
experienced  and  interested  in  steel  working.  Wrought  iron  is  less 
affected  by  overheating  because  it  has  no  carbon  to  be  burned  out, 
and  is  not  subject  to  the  internal  crystalline  conditions  to  anything 
like  the  degree  affecting  steel,  if  at  all. 

295.  Terms  Commonly  Used  in  Forging. — Among  the  terms  used 
may  be  mentioned  the  following : 

(1)  Upsetting  is  the  increase  in  thickness  and  decrease  in  length 
produced  by  hammering  a  hot  piece  of  metal  on  the  end.     Up- 
setting is  resorted  to  for  forging  bolt  heads,  and  for  forming  a 
bulk  of  metal  as  ample  stock  for  further  heating  and  hammering 
operations  in  welding,  etc. 

(2)  Drawing  out  is  the  opposite  of  upsetting  and  is  used  when 
work  is  to  be  pointed  or  made  smaller  in  cross-section. 

(3)  Scarfing  is  the  tapering  of  two  ends  of  metal  so  that  they 
may  fit  together  at  their  surfaces  of  contact  as  if  one  continuous 
piece. 

(4)  Swaging  is  the  reducing  of  cross-section,   and  finally  the 
shaping  and  finishing  a  bar  or  rod  by  use  of  the  swage  block  or  by 
use  of  the  top  and  bottom  swages  on  the  anvil. 


THE  BLACKSMITH  SHOP 


267 


296.  Measuring  Stock  for  Forging.— Fig.  144  shows  two  dimen- 
sioned sketches  such  as  would  be  given  a  blacksmith  for  making  an 
angle  and  a  ring.    To  cut  stock  to  the  exact  length  for  the  angle,  take 
the  length  of  the  neutral  axis  ab,  which  is  practically  15  inches,  in  this 
case.  Likewise,  stock  for  the  ring  is  cut  to  a  length  equal  to  the  length 
of  the  neutral  axis  plus  an  amount  needed  for  scarfing  and  lapping 
for  a  weld.    In  homogeneous  bars  or  plates  of  malleable  metals,  the 
neutral  axis  is  practically  in  the  middle  plane,  and  bending  stretches 
metal  on  one  side  of  this  plane  about  as  much  as  it  compresses  metal 
on  the  other  side. 

297.  Welding. — This  process  of  joining  together  two  pieces  of 
iron  has  long  been  practiced  in  blacksmith  ing,  but  is  now  by  no 
means  confined  to  the  blacksmith  shop  nor  to  the  metal  used  therein. 


In  welding  wrought  iron  or  mild  steel  in  the  blacksmith  shop, 
care  is  required  to  heat  both  pieces  evenly.  Mild  steel  must  be  heated 
and  worked  with  skill  and  judgment  in  welding,  as  its  temperature 
range  between  the  time  it  becomes  cohesive  and  the  time  it  melts  or 
begins  to  oxidize  rapidly  is  not  as  great  as  the  corresponding  tem- 
perature range  of  wrought  iron. 

To  assist  welding  a  flux  is  used.  The  surfaces  of  metals  brought 
to  a  welding  heat  are  unavoidably  oxidized  more  or  less,  i.  e.,  scale 
is  formed  on  them.  If  this  is  allowed  to  remain,  it  prevents  contact 
of  metal  to  metal,  thus  preventing  a  weld.  The  flux  is  sprinkled 
in  the  ends  at  about  a  yellow  heat.  This  melts  and  forms  a  film 
over  the  hot  metal  protecting  it  against  further  oxidation  and  caus- 
ing the  oxide  formed  to  melt  at  a  low  heat.  The  liquid  oxide  and 
flux  are  readily  displaced  as  the  metal  is  hammered  into  contact. 
Scale  formed  on  wrought  iron  melts  at  about  its  welding  tempera- 
ture, hence  some  smiths  may  not  use  flux  for  wrought-iron  welding. 


268 


MECHANICAL  PROCESSES 


Fluxes  commonly  used  are  silica  (sand),  borax,  or  sal  ammoniac. 
A  borax  flux  should  be  first  fused  to  get  rid  of  its  water  of  crystaliza- 
tion  and  then  it  does  not  bubble  when  powdered  and  sprinkled  on 
the  hot  metal. 

Anvil  welding  requires  preliminary  shaping  of  the  two  surfaces 
to  be  welded.  The  forms  of  welds  much  used  are  as  follows: 

(1)  Faggot  weld.  A  frequent  example  of  faggot  welding  is  that 
used  to  make  a  large  mass  of  metal  in  a  bar  as  shown  by  the  doubled 
part  in  Fig.  14.5. 


FIG.  145. 


FIG.  146. 


(2)  Lap  weld.  Fig.  146  shows  the  ends  of  two  pieces  prepared 
for  a  lap  weld.  Their  contact  surfaces  are  made  convex  to  force 
out  any  scale  or  dirt  as  the  weld  is  hammered  together. 


FIG.  147. 

(3)  Link  weld.     This  is  a  lap  weld  much  used  in  chain  links, 
eye  bolts  and  ring  welding,  and  is  shown  at  a,  Fig.  147. 

(4)  Butt  weld.    The  two  pieces  are  shaped  with  convex  ends  as 
shown  at  ~b,  Fig.  147. 

(5)  Split  weld  for  thin  material.    The  form,  shown  at  c,  is  used 
because  the  two  pieces  can  be  jammed  together  quickly  on  drawing 
them  from  the  fire  and  hammered  without  loss  of  time,  as  the  pieces 
cool  quickly. 

(6)  Split  weld  for  heavy  material.     Pieces  shaped  for  this  weld 
(d,  Fig.  147)   give  much  bearing  surface  within  a  small  radius. 
This  is  much  used  in  welding  together  wrought  iron  and  mild 


THE  BLACKSMITH  SHOP  269 

steel.  A  bulk  of  metal  holds  its  heat  longer  for  welding,  and  much 
bearing  surface  gives  a  greater  per  cent  of  strength  of  the  weld  as 
compared  to  the  strength  of  the  solid  piece. 

(7)  T  weld.  The  pieces  for  this  weld  are  shaped  as  shown  at  g, 
Fig.  147. 

298.  Hardening  and  Tempering  at  the  Forge. — The   forging, 
hardening  and  tempering  of  steel  tools  for  cutting  metals  have  long 
been  practiced  as  a  part  of  blacksmithing.     The  process  used  by 
blacksmiths  to  give  an  edged  tool  the  correct  degree  of  hardness  is 
accomplished  in  two  steps  vaguely  designated  as  "  tempering."    To 
illustrate  blacksmith-shop  hardening  and  tempering,  which,  though 
crude,  is  highly  useful  and  very  convenient,  an  example  of  hardening 
and  tempering  a  cold  chisel  will  be  given : 

Having  forged  the  cutting  end  to  shape,  place  this  end  in  the  fire 
and  heat  about  half  the  length  of  the  chisel  to  cherry  red  (the 
critical  temperature,  as  near  as  can  be  judged).  Plunge  most  of 
the  red  hot  part  into  water,  holding  it  still  until  cold,  then  with- 
draw and  quickly  rub  a  bright  metallic  spot  near  the  cutting  edge 
with  a  piece  of  grindstone  or  other  abrasive  material.  This  quench- 
ing gives  the  cutting  end  the  maximum  hardness  which  can  be 
given  it,  but  this  is  too  hard  for  use,  and  the  heat  left  in  the  un- 
quenched  part  of  the  chisel  is  now  used  for  the  purpose  of  tempering 
this  extreme  hardness,  or  "  drawing  the  temper." 

Holding  the  chisel  in  the  tongs,  watch  the  gradual  changes  of 
color  on  the  rubbed  spot,  as  the  heat  travels  down  from  the  un- 
quenched  end.  As  soon  as  the  color  reaches  that  denoting  the  hard- 
ness desired  (dark  purple  in  this  case),  plunge  the  whole  chisel  at 
once  into  water  to  prevent  further  "  drawing  of  temper." 

The  water  must  not  be  extremely  cold,  as  the  sudden  change  of 
temperature  may  be  great  enough  to  cause  small  cracks  over  the 
surface  of  the  steel. 

299.  Color  Table  for  Judging  Hardness. — The  first  color  observed 
after  rubbing  a  bright  spot  on  a  piece  of  quenched  steel  is  a  light 
straw,  denoting  the  greatest  degree  of  hardness  possible  for  that 
particular  piece  of  steel.    As  the  heat  travels  into  the  quenched  end, 
the  hardness  decreases,  as  denoted  by  the  change  of  colors  in  the 
order  of  light,  medium  and  dark  straw,  light  and  dark  purple,  dark 
and  light  blue.    These  colors  are  temperature  indicators,  and  as  the 

18 


270  MECHANICAL  PROCESSES 

reduction  in  hardness  of  the  steel  is  dependent  upon  the  amount  of 
annealing  which  the  hardened  end  gets  from  the  heat  in  the  other 
end,  these  colors  correspond  with  degrees  of  relative  hardness  in 
regular  order.  A  color,  purple  for  example,  does  not  indicate  the 
same  degree  of  hardness  in  all  grades  of  carbon  steels,  as  the  hard- 
ness in  different  carbon  steels  at  a  given  temperature  depends  upon 
the  contained  carbon. 

300.  Hardening  of  Alloy-Steel  Tools. — The  alloy  steels  are  so 
various  in  composition  that  no  general  rule  can  be  given  for  their 
hardening.     The  best  method  is  to  follow  the  directions  given  by 
the  maker  of  each  grade  of  this  steel,  and  not  attempt  to  harden 
all  grades  by  the  method  one  may  be  familiar  with  for  hardening  any 
particular  alloy.    However,  many  alloy  steels  are  hardened  by  heat- 
ing to  a  white  heat  and  cooling  in  a  blast  of  air — less  rapidly  than 
by  quenching. 

301.  Influence  of  the  Cooling  Medium  in  Hardening. — The  prac- 
tice of  using  water,  brine,  oil  and  other  liquids  for  quenching  a  steel 
tool  after  heating  for  hardening,  varies  with  different  blacksmiths. 
As  was  previously  mentioned,  two  of  the  factors  controlling  the 
hardness  of  a  piece  of  quenched  steel  are  the  rapidity  of  cooling 
and  the  range  of  temperature  through  which  cooled.     These  may 
be  combined  as  one  condition,  viz.,  the  range  of  temperature  through 
which  a  piece  of  steel  is  cooled  in  a  given  time.     In  any  cooling 
liquid  this  condition  depends   (1)  upon  the  difference  in  tempera- 
ture of  the  steel  and  the  liquid,  and   (2)   upon  the  rapidity  with 
which  the  liquid  will  conduct  away  the  heat  imparted  to  it  by  the 
metal.    It  is  seen  that  the  2d  item  depends  upon  the  ability  of  the 
liquid  as  a  conductor  of  heat,  upon  its  specific  heat,  and  whether 
or  not  its  vapor  forms  around  the  hot  metal  or  whether  a  sticky 
film,  as  of  oil,  forms  around  the  metal  from  charring.     Experience 
is  best  to  determine  all  these  factors,  and  there  is  no  mysterious 
virtue  about  any  of  the  cooling  media. 

302.  Annealing   in   the   Blacksmith   Shop. — Occasionally    it   is 
necessary  to  take  the  temper  from  a  piece  of  tool  steel  for  forging 
into  another  shape,  i.  e.,  the  steel  is  to  be  softened.     It  is  heated 
to  a  red  heat  and  is  placed  between  two  heavy  pieces  of  pine  board. 
Weighted  down,  or  pressed  together  in  a  vise,  the  steel  soon  burns 
a  cavity  in  the  wood,  and  as  the  two  boards  come  together  they  com- 


THE  BLACKSMITH  SHOP 

pletely  bury  the  steel,  shuting  off  all  oxygen  and  stopping  further 
burning.  The  charred  wood  surrounding  the  steel  allows  it  to  cool 
only  very  slowly,  and  in  a  few  hours  the  metal  is  cold  and  soft. 

A  red  hot  piece  of  steel  may  be  softened  by  burying  it  in  hot  sand. 
The  object  is  slow  and  even  cooling.  Some  alloy  steels  cannot  be 
softened  by  any  known  means  after  they  are  once  hardened. 

303.  Equipment  of  the  Forge  Shop. — As  this  part  of  the  black- 
smith shop  is  intended  for  heavy  work  its  principal  equipment  is 
one  or  more  steam  hammers  of  the  small  single  frame  type  or  of  the 
heavy  double  frame  type.     Other  essential  equipment  includes: 

(2)  Tools  and  holding  appliances  to  assist  in  shaping  the  forging 
and  in  holding  the  billet  forged. 

(3)  A  suitable  furnace,  preferably  oil  or  gas  fired,  for  heating 
billets. 

(4)  An  upsetting  machine  (not  always  installed)   which  works 
much  like  a  rivet-heading  machine  in  squeezing  a  length  of  red-hot 
metal  into  a  shorter  and  larger  bulk. 

304.  The   Steam  Hammer. — Steam  hammers   are  single  acting 
when  the  hammer  is  raised  by  steam  and  falls  by  gravity  alone;  or 
are  double  acting  when  the  hammer  is  raised  and  forced  down  by 
steam. 

The  smaller  hammers  have  single  frames  and  the  larger  hammers, 
as  shown  in  Fig.  1-48,  have  double  frames.  This  view  shows  a 
2500-lb.  hammer,  i.  e.,  one  whose  hammer  and  moving  parts  at- 
tached thereto  weigh  2500  Ibs. 

The  hammer  H  is  raised  and  forced  down  by  steam  acting  on  a 
piston  in  the  cylinder  C.  One  of  the  levers  at  the  side  governs  the 
steam  supply  to  the  hammer,  and  the  other  controls  the  rapidity 
and  force  of  the  blows.  The  hammer  oscillations  synchronize  with 
the  controlling  lever  movements,  and  an  experienced  man  or  boy 
can  regulate  the  force  of  the  Wow  with  great  nicety.  The  dies  DD 
are  keyed  to  the  hammer  and  to  the  anvil  cap  A. 

305.  Appliances  Used  with  the  Steam  Hammer. — Blooms  and 
large  billets  are  held  during  forging  by  a  chuck  and  porter  bar,  or 
by  a  porter  bar  clamped  to  one  end  of  the  forging.    Smaller  billets 
are  gripped  by  heavy  tongs  made  to  conform  to  the  size  of  the 
billet  end.    The  combined  weight  of  billet  and  tongs  is  balanced  in 
the  loop  of  an  endless  chain  hung  from  the  crane. 


272 


MECHANICAL  PROCESSES 


The  principal  steam-hammer  tools  are  as  follows,  shown  in  Fig. 
149: 

(1)  The  hammer-chisel,  for  cutting  hot  iron  nearly  in  two  from 
one  side. 

(2)  The  snapping  bar,  round  at  one  end  and  triangular  at  the 
other  end,  for  finishing,  from  the  opposite  side  the  cutting  begun 


FIG.  148. — Steam  Hammer. 

by  the  hammer-chisel.     To  cut  completely  through  with  the  chisel 
would  injure  the  chisel  against  the  anvil. 

(3)  The  necking  tool,  for  making  a  square  or  filletted  shoulder. 

(4)  The  fuller  bar,   a  round   bar   for  reducing  and   grooving 
forgings. 

(5)  The  tapering  and  fullering  tool,  used  as  shown  at  5a. 


THE  BLACKSMITH  SHOP 


273 


(6)  The  set,  a  square  bar  for  squaring  corners  in  narrow  parts 
of  a  forging. 

(7)  The  spring  swage. 

(8)  The  punch. 

A  tool  is  held  against  the  forging  and  it  receives  the  blows  of 
the  hammer.  The  handles  of  these  tools  are  from  3  to  6  feet  long, 
of  iron. 


FIG.  149. — Steam  Hammer  Tools. 

306.  Heating  Furnaces. — The  open  forge  is  not  well  adapted  to 
steam-hammer  work,  but  some  form  of  closed  furnace  is  necessary 
to  give  the  required  amount  of  concentrated  heat.  Oil,  gas  or  coal 
furnaces  are  much  used,  with  preference  for  the  oil  furnace  be- 
cause of  its  ready  control.  Oil  furnaces  of  similar  type  to  that 
shown  in  Fig.  50,  but  usually  smaller,  are  well  adapted  to  forge 
shop  use. 


274  MECHANICAL  PROCESSES 

307.  Notes  on  Steam-Hammer  Forging. 

(1)  Upsetting  in  large  forge  work  may  be  done  by  holding  the 
heated  billet  between  the  hammer  and  the  anvil  dies  and  bumping 
it  with  a  battering  ram  known  as  a  "  tup  "  or  "  monkey."    This  is  a 
heavy  mass  of  iron  with  a  smooth  end  and  a  long  horizontal  handle. 
It  is  suspended  from  the  roof,  and  is  swung  like  a  pendulum  so  that 
it  strikes  the  billet  on  end. 

(2)  Metal  should  be  forged  only  at  a  red  heat,  though  light 
blows  for  surface  finishing  may  safely  be  given  at  a  blue  heat. 
Forging  nearly  cold  iron  is  not  advantageous  and  iron  so  forged 
should  be  annealed. 


FIG.  150. 

(3)  The  energy  in  a  small  hammer  forced  at  high  speed  against 
a  forging  may  be  made  the  same  as  that  in  a  large  hammer  forced 
at  a  lower  speed,  but  the  effect  of  the  blow  on  the  forging  is  not  the 
same.    A  quickly  delivered  blow  is  superficial  in  its  effect,  while  a 
slowly  delivered  blow  from  a  heavy  hammer  is  more  like  the  squeeze 
of  the  hydraulic  press,  and  is  deeper  felt.     The  particles  of  metal 
have  time  to  re-arrange  themselves  under  the  slower  speed  of  the 
heavy  hammer. 

(4)  The  effects  of  cold  or  hot  forging,  and  of  light  or  heavy 
hammers  as  mentioned  in  items  (2)   and  (3)   are  often  shown  in 
finished  forgings,  sometimes  to  the  extent  of  damaged  parts.     For 
example1,  the  piece  A,  Fig.  150,  shows  how  the  edge  of  a  forging 
looks  which  is  forged  at  a  good  working  heat  and  the  hammer 
blows  are  felt  entirely  through  the  piece.    B  shows  that  the  forging 
was  not  hot  enough,  or  the  hammer  was  too  light,  or  both. 


CHAPTER  XI. 
THE  MACHINE  SHOP. 

308.  Scope    of    Machine-Shop    Work. — The    machine    shop    is 
equipped  for  the  work  of  finishing  castings  and  forgings  to  exact 
form  and  dimensions.     This  work  is  done  principally  by  means 
of  machine  tools  which  cut  off  superfluous  metal,  and  to  a  far  less 
degree  by  chipping,  filing,  and  scraping  with  hand  tools. 

In  addition  to  finishing  castings  and  forgings,  there  are  made  in 
the  machine  shop  many  articles  for  particular  or  general  use  from 
bars  of  iron,  steel,  brass  and  bronze  supplied  from  the  rolling  mill. 

An  important  supplementary  work  of  this  shop  is  that  of  assem- 
bling the  finished  parts  of  an  engine  or  other  machine  and  fitting 
them  together  in  complete  form  ready  for  use.  This  assembling 
is  done  in  the  erecting  shop  where  all  parts  composing  a  machine 
are  brought  to  a  final  adjustment. 

It  will  be  noticed  that  the  word  "  work  "  is  much  used  in  the 
machine  shop  to  designate  a  forging,  casting,  or  other  piece  of 
metal  to  be  machined,  i.  e.,  finished  to  shape  by  means  of  machine 
tools. 

309.  Machine-Shop  Practice. — The  time  required   for  work   of 
such  accuracy  as  is  done  in  the  machine  shop,  and  the  high  cost  of 
skilled  labor  for  efficient  work  makes  machine  shop  processes  very 
expensive — often  excessively  so.     Modern  competition  has  brought 
close  attention  to  the  desirability  of  avoiding  machine-shop  work 
and  of  doing  what  can  be  done  to  save  time  and  labor  where  this 
grade  of  work  cannot  be  obviated. 

To  avoid  machine-shop  expense,  particular  effort  is  now  directed 
to  making  castings  smoother,  and  many  metal  articles  shaped  by 
cold  or  hot  pressing  are  used  in  place  of  machine-shop  products 
cut  from  solid  metal. 

In  the  machine  shop,  the  work  of  which  is  not  likely  to  wane 
in  this  age  of  metal,  particular  attention  is  given  (1)  to  placing 
at  the  disposal  of  the  highly  skilled  machinist  such  drawings,  tools, 


276  MECHANICAL  PROCESSES 

appliances,  machines  and  attachments  as  will  enable  him  to  ac- 
complish most  in  a  given  time,  and  (2)  to  employing  perfected 
machines,  tools,  etc.,  so  that  efficient  metal  cutting  may  progress 
at  as  rapid  a  speed  as  possible. 

Modern  practice  requires  that  drawings  be  made  clear  and 
amply  dimensioned,  tools  be  of  highest  quality  and  kept  ready  for 
use,  machines  be  kept  clean  and  adjusted,  and  in  short  that  every 
movement  of  the  highly  skilled  men  be  toward  accomplishing 
something  definite  in  furthering  work  and  that  all  unnecessary 
movements  be  eliminated.  To  carry  out  so  refined  a  system,  the 
highly  paid  machinist  must  be  directed  in  the  best  methods  for 
doing  a  given  piece  of  work  by  an  efficient  and  experienced  shop 
superintendent,  and  all  that  can  be  done  through  preliminary 
preparations  or  otherwise  by  less  expensive  labor  is  done  to  save 
the  time  of  the  highly  paid  man.  The  highly  paid  men  are  selected 
and  developed  because  of  their  aptitude  for  their  work,  and  judg- 
ment must  be  exercised  in  their  selection. 

Much  has  been  written  on  the  determination  of  the  practical 
rate  at  which  metals  can  be  cut,  and  no  little  value  has  been  de- 
rived from  efforts  along  this  line.  It  may  be  said  that  a  machine 
should  be  run  at  as  great  a  cutting  speed  as  the  work,  the  tool,  and 
the  machine  will  safely  stand  in  continued  practice. 

It  is  well  to  understand  that  there  are,  in  machine-shop  work, 
different  degrees  of  refinement  in  cutting  down  and  finishing  to 
exact  dimensions,  according  to  the  different  degrees  of  error  in- 
cident to  various  methods  and  classes  of  machines. 

310.  Machine-Shop  Equipment. — The  equipment  of  a  machine 
shop  naturally  depends  upon  the  size  and  variety  of  work  it  has  to- 
do.  There  are  different  sizes  of  machines  of  the  same  kind  for 
machining  different  sizes  of  castings  and  forgings,  also  there  are 
different  kinds  of  machines  for  doing  the  same  kind  of  work  in 
different  grades  of  refinement.  An  economic  consideration  is  to 
have  as  few  machines  as  possible  to  do  as  great  a  range  of  work 
as  possible,  and  this  is  best  accomplished  by  choosing  high-grade 
machines  which  are  not  only  adapted  to  variety  of  work,  but  are 
also  able  to  stand  the  durable  test  of  producing  good  work  in 
minimum  time.  Fig.  151  shows  the  general  arrangement  of  a 
large  machine  shop. 


THE  MACHINE  SHOP 


277 


278  MECHANICAL  PROCESSES 

The  metal-cutting  machines  of  a  machine  shop  are  known  as 
machine  tools  and  the  work  done  by  them  is  known  as  machining. 
The  principal  equipment  of  the  machine  shop  is  as  follows: 

(1)  Several  types  of  machine  tools,  and  their  cutting  tools. 

(2)  Vise  benches  equipped  with  suitable  vises  for  hand  work 
and  tools  for  chipping,  filing,  scraping,  hand-thread  cutting,  etc. 

(3)  Small  tools  for  measuring,  trying,  adjusting,  etc. 

(4)  A  laying-off  table,  also  called  a  marking-off  table  for  laying 
out  and  marking  work  preparatory  to  machining  it. 

(5)  Portable  tools  worked  by  hand  or  driven  by  compressed  air 
or  electric  power. 

(6)  Crane   and   other   appliances   for   lifting   and  transporting 
heavy  work. 

(7)  A  tool  room  where  all  tools  are  kept  when  not  in  use. 

311.  Marking  Work  to  be  Machined. — An  important  prelimi- 
nary in  a  machine  shop  is  the  lying  off  and  marking  of  work. 
Forgings,  castings  and  other  work  to  be  machined  must  be  marked 
to  indicate  the  location  of  holes  to  be  drilled,  the  axis  or  axes  of 
hollow  parts  to  be  bored  out,  and  in  general  the  limits  which 
guide  the  machinst  in  cutting  away  superfluous  metal  to  bring 
the  work  to  the  finish  and  dimensions  required  by  the  draw- 
ing. For  example,  Fig.  152  shows  a  casting  of  two  small  cylin- 
ders cast  in  a  single  piece  for  a  steam-launch  engine.  This 
casting  is  in  the  rough  just  as  it  was  received  from  the  foundry. 
The  two  pieces  of  wood  WW  have  been  placed  in  the  cylinder  ends 
to  aid  in  marking.  The  casting  must  be  so  marked  that  the 
machinist  can  bore  the  cylinders  to  bring  the  axes  the  required 
distance  apart,  face  the  cylinder  ends  to  give  the  cylinders  the 
required  length,  and  in  short  machine  off  all  surfaces  which  re- 
quire machining,  and  drill  all  holes,  as  required  by  the  drawing. 

The  marking  must  be  done  from  some  point,  line  or  plane  of 
reference  which  is  usually  chosen  to  agree  with  the  axes  of  refer- 
ence shown  on  the  drawing.  From  this  point,  line,  or  plane,  all 
holes  and  machined  surfaces  are  located  on  the  work. 

In  the  casting  here  shown  a  plane  of  reference  is  chosen  which 
includes  the  axes  of  the  cylinders  as  determined  by  the  outer 


THE  MACHINE  SHOP 


279 


surfaces  of  the  cylinders.  This  plane  is  located  on  the  casting  by 
the  line  KLMK,  which  completely  girdles  the  casting.  The  line  is 
scratched  by  a  scriber  and  further  marked  at  intervals  by  the 
center  punch  to  avoid  its  obliteration.  The  axes  of  the  two  cylin- 
ders are  then  located  and  marked  by  aid  of  the  wood  pieces  W, 
and  from  these  axes  all  other  marks  are  located.  All  dimensions 
are  supplied  by  the  drawings. 


FIG.  152. — Casting  Marked  for  Machining. 

Castings  and  forgings  are  often  whitewashed  or  chalked  where 
their  reference  planes  are  to  be  marked,  as  this  helps  the  workmen 
to  see  the  marks  readily. 

The  machining  on  the  casting  here  shown  is  begun  by  planing 
the  face  J\1G  and  then  the  face  LK  of  the  two  steam  chests.  These 
finished  surfaces  give  convenient  parallel  planes  for  the  transfer 
of  measurements.  Also  the  face  MG  forms  a  base  for  securing  the 
casting  on  the  machine  which  bores  the  two  cylinders. 

312.  The  Marking-Off  Table. — To  afford  means  for  marking 
work  accurately  preparatory  to  machining  it,  a  marking-off  table  is 
provided.  Certain  measuring  and  marking  tools,  and  suitable 
blocks  for  supporting  the  piece  to  be  marked,  must  also  be  provided. 


280 


MECHANICAL  PROCESSES 


Fig.  153  shows  a  small  marking-of?  table  made  of  a  ribbed  slab 
of  cast  iron  supported  firmly  on  four  posts.  The  top,  sides  and 
ends  of  the  slab  are  planed  smooth  and  at  right  angles  one  to 
another.  The  table  is  placed  in  a  permanent  location  in  the  shop, 


FIG.  153.— Marking-Off  Table. 

where  it  is  firmly  supported,  and  its  top  is  adjusted  accurately 
horizontal. 

For  very  large  work,  a  table  may  be  made  of  several  slabs  placed 
at  or  near  the  floor  level  and  supported  on  a  foundation  especially 
built  to  hold  them  level. 


FIG.  154.— Chocks  of  Marking-Off  Table. 

313.  Tools  and  Appliances  for  the  Marking-Off  Table. — To  sup- 
port a  piece  of  work  so  that  its  chosen  plane  of  reference  may  be 
parallel  or  perpendicular  to  the  top  of  the  table,  a  number  of 
chocks  and  bars  are  used.  Fig.  154  shows  specimens  of  chocks  C 
and  of  rectangular  bars  B.  These  are  used  in  pairs  and  each  pair 
must  be  exact  counterparts. 


THE  MACHINE  SHOP 


281 


Among  the  tools  much  used  on  the  marking-off  table  are  the 
following : 

(1)  Steel  rule  (Fig.  155).  Made  in  various  lengths.  Opposite 
faces  and  edges  are  ground  parallel. 


*    J^ 


FIG.  155. 

(2)  Straight  edge.  A  long  steel  rule  without  graduations. 
Used  to  test  plane  surfaces  and  to  establish  straight  lines  as  refer- 
ences for  measurements. 


FIG.  156.  FIG.  157. 

(3)  Combination  level  and  square  (Fig.  156.)   Used  as  a  square 
and  a  level.    The  auxiliary  center  head  is  used  to  locate  the  centers 
of  cylindrical  work.     The  ordinary  steel  square  is  also  much  used. 

(4)  Dividers  (Fig.  157). 


Outside. 

FIG.  158. 

(5)   Firm-  joint  calipers  (Fig.  158). 
thicknesses,  etc. 


Inside. 


For  measuring  diameters, 


FIG.  159.  FIG.  160. 

(6)  Center  punch  (Fig.  159).    This  marks  holes  to  be  drilled, 
and  marks  points  for  locating  lines  on  work. 

(7)  Scribers  (Fig.  160).     These  have  hardened  steel  points  for 
scratching  lines  on  metal. 


282 


MECHANICAL  PROCESSES 


(8)  Surface  gage  (Fig.  161).  This  is  used  in  adjusting  work 
on  the  marking-off  table,  and  for  locating  points  or  lines  on  the 
work.  It  consists  essentially  of  a  base,  a  post  and  a  scriber.  The 
under  side  of  the  base  is  planed  to  rest  firmly  on  the  table,  and  is 
grooved  to  rest  symmetrically  on  a  cylindrical  surface.  The  scribei 
and  post  are  so  mounted  and  controlled  by  clamp  screws  that  the 


FIG.  161. 

scriber  points  may  be  adjusted  to  any  position  desired  within  the 
reach  of  the  instrument. 

314.  Refined  Measuring  in  Machine  Work. — The  machine  shop 
is  the  shop  on  which  devolves  the  requirement  of  finishing  work  to 
specified  dimensions  within  very  small  limits  of  allowable  error. 

The  discerning  of  small  differences  in  physical  measurements 
is  dependent  upon  the  degree  of  refinement  of  measuring  instru- 


THE  MACHINE  SHOP  283 

ments,  upon  variations  of  temperature,  and  upon  the  delicacy  of 
the  sense  of  touch. 

All  products  turned  out  by  the  machine  shop  do  not  require  the 
same  degree  of  exactness  in  finished  dimensions,  and  it  would  be  a 
needless  expense  to  finish  all  work  with  the  same  high  degree  of 
precision  required  for  some  grades  of  work.  Most  of  the  refined 
finishing  to  a  particular  dimension  is  done  not  closer  than  T^V<j 
of  an  inch.  A  drawing  of  a  piece  of  work  which  is  to  be  finished 
with  especial  care  for  making  a  close  fit  must  state  limits  of  error 
allowable  and  on  which  side  of  the  given  dimension  this  is  allowed. 

A  wheel  hub  may  be  forced  or  driven  tightly  on  its  shaft.  This 
is  a  driving  or  forcing  fit.  If  the  hole  in  the  hub  is  bored  slightly 
smaller  than  the  diameter  of  the  shaft,  the  hub  may  be  expanded 
by  heat  until  it  fits  over  the  shaft.  On  cooling  it  grips  the  shaft 
and  makes  a  shrinkage  fit.*  A  shaft  may  fit  more  or  less  closely  in 
the  bearing  in  which  it  revolves.  If  the  fit  is  not  too  tight  to 
prevent  free  motion,  it  is  called  a  working  or  sliding  fit. 

Forcing  fits  are  made  by  hydraulic  forcing  presses,  or  by  the 
pull  of  heavy  bolts. 

The  degree  of  refinement  necessary  in  a  working  fit  for  any 
moving  part  of  a  machine  depends  upon  the  size  and  degree  of 
refinement  needed  in  the  machine.  The  main  bearing  of  a  marine 
engine  is  usually  adjusted  to  about  .012  inch.  The  main  spindle 
of  a  machine  lathe  is  about  .002"  smaller  than  the  bearing  in  which 
it  revolves,  and  a  very  accurate  grinding  machine  is  adjusted  as 
close  as  the  metal  of  a  carefully  ground  shaft  and  bearing  can 
come  together  without  gripping. 

315.  Tools  for  Measuring. — The  steel  rule  is  the  simplest  form 
of  measuring  tool  used  in  the  machine  shop.  It  cannot  be  used, 
however,  for  measuring  lengths  smaller  than  can  readily  be  dis- 
cerned by  the  eye.  For  such  measurements  various  forms  of 
calipers  and  gages  are  used.  The  accuracy  of  these  depends  upon 
the  sense  of  touch. 

*  A  table  of  allowances  for  forcing  and  for  skrinkage  fits  is  given  in 
Par.  441,  Appendix. 


284 


MECHANICAL  PROCESSES 


The  various  forms  of  calipers  and  gages  for  accurate  measuring 
are  as  follows : 

(1)   Firm-joint  calipers  (Fig.  158). 


Outside. 


Inside. 


FIG.  162. 


(2)  Screw-adjusting  calipers  (Fig.  162) 

(3)  Spring  calipers  (Fig.  163). 


Outside. 


Inside. 


FIG.  163. 


(4)   Inside  gages    (Fig.   164).     This   instrument  consists  of  a 
sleeve  which  holds  rods  of  different  lengths  for  measuring  inside 


FIG.  164. 


diameters  of  large  cylinders.     A  threaded  nipple  on  one  end  of  the 
sleeve  provides  a  means  for  fine  adjustments. 


FIG.  165. 


(5)   Depth  gages  (Fig.  165).     For  measuring  depths.    The  slid- 
ing head  is  clamped  on  the  rule  at  the  point  which  marks  the  depth. 


THE  MACHINE  SHOP 


285 


(6)  Fixed  gages.  Fig.  1G6  shows  one  of  several  forms  of  fixed 
gages  for  measuring  diameters  within  certain  limits  of  error.  The 
gage  here  shown  is  for  measuring  a  hole  of  1"  diameter,  with  an 


FIG.  166. 


allowable  error  of  plus  or  minus  .001".    The  end  marked  .999  should 
go  through  the  hole;  that  marked  1.001  should  not  enter  the  hole. 


tWs^jSg^iVs^gV-1' ?*'•»«'•« 
444^!5HlH'?°io>vi«^' 

0|slI<feo?<ko?0=050iOiO:OIOi:O;O:O-O5tef 

I  i  to;  6: 6;  6  •  6-  6=  5;  5;  5-  5-  6-  o^ 


FIG.  167. 


FIG.  168. 


(7)   Micrometer  caliper. 
Fig.  170. 


Adjustable  for  refined  measuring.    See 


FIG.  169. 

Closely  akin  to  the  tools  just  mentioned  are  others  much  used  in 
the  machine  shop.     A  list  of  them  includes  the  following: 

(8)  Protractor  for  measuring  angles  (Fig.  167). 

(9)  Drill  gage  (Fig.  168).     For  measuring  diameters  of  drills. 

(10)  Wire  and  sheet-metal  gage  (Fig.  169). 
19 


286  MECHANICAL  PROCESSES 

316.  The  Micrometer  Caliper. — This  instrument,  a  type  of  which 
is  shown  in  Fig.  170,  is  used  for  measuring  thicknesses  and  external 
diameters.  It  is  the  instrument  of  the  greatest  degree  of  precision 
used  in  machine-shop  measuring. 

Most  micrometer  calipers  are  made  to  show,  on  a  graduated  stem 
or  barrel,  readings  of  measurements  to  T-^TT  °^  an  incn>  or  to  y-g-g- 
of  a  millimeter  if  graduated  in  the  metric  system.  Some  of  these 
instruments  are  supplied  with  verniers  for  showing  readings  vary- 
ing by  Toinnr  °^  an  incn>  but  measurements  of  less  than  y-^oir  °^  an 
inch  are  seldom  used. 

Material  is  measured  between  the  points  B  of  hardened  steel, 
one  of  which  is  fixed  in  the  half-round  frame.  The  enclosed  end 
of  the  spindle  C  is  screwed  into  a  fixed  sleeve  A,  and  when  the 


FIG.  170. — Micrometer  Caliper. 

spindle  is  turned,  its  threads  cause  it  to  move  in  the  direction  of 
its  length.  These  threads  have  a  pitch  of  40  to  an  inch,  hence  one 
turn  of  the  spindle  moves  it  -fa  of  an  inch.  The  sleeve  A  is  about 
as  long  as  the  distance  between  the  ends  of  the  frame.  A  hollow 
thimble  D  fits  neatly  over  the  sleeve,  and  the  right-hand  end  of  the 
spindle  is  fastened  to  the  bottom  of  the  thimble  so  that  the  thimble 
is  used  to  turn  the  spindle  and  to  gage  its  movements. 

The  tapered  edge  of  the  thimble  is  divided  around  its  circumfer- 
ence into  25  equal  parts,  and  a  line  along  the  sleeve  A  is  graduated 
into  divisions  of  TV  of  an  inch.  The  first  of  these  graduations  is 
marked  zero. 

When  the  space  between  the  measuring  points  is  closed,  the  zero 
line  on  the  edge  of  the  thimble  falls  on  the  line  along  the  sleeve, 
and  as  the  thimble  is  turned  ^  of  a  revolution  (or  one  of  the 


THE  MACHINE  SHOP  287 

graduations  on  its  edge)  it  separates  the  points  -fj  °f  3TT  =  rnnnr 
of  an  inch.  In  this  way  the  readings  of  T¥Vo  °^  an  incn  are 
observed. 

Micrometer  gages  similar  to  Fig.  164  are  made  for  refined 
measurement  of  internal  diameters. 

317.  Machine  Tools. — A  list  of  machine  tools  for  a  well-equipped 
shop  is  as  follows: 

(1)  Lathe. 

(2)  Drilling  machine,  commonly  called  a  drill. 

(3)  Planer. 

(4)  Shaping  machine  or  shaper. 

(5)  Milling  machine. 

(6)  Boring  machine  or  boring  mill. 

(7)  Slotting  machine. 

(8)  Pipe  cutting  and  threading  machine. 

(9)  Tool-sharpening  equipment. 

(10)  Metal  saws. 

(11)  Forcing  presses. 

There  are  several  sizes  and  types  of  each  of  these  classes  of 
machines.  The  differences  in  the  several  types  of  one  class  consist 
of  durability  of  make,  rapidity  and  degree  of  accuracy  of  work 
done,  and  range  of  adaptability  to  various  kinds  of  work. 

Some  shops  may  have  machines  other  than  those  here  named  for 
special  or  unusual  work,  though  many  shops  have  only  Nos.  1,  2, 
3,  4,  5  and  9,  and  even  a  considerable  variety  of  work  can  be 
managed  with  lathe,  drill  and  planer. 

The  best  means  of  driving  machine  tools  is  by  means  of  an 
electric  motor  for  each  machine. 

318.  The  Lathe. — In  this  machine,  as  in  the  wood  lathe,  work 
revolves  about  a  fixed  axis  between  the  centers   and  the  cutting 
tool  moves  either  (1)  parallel  to  the  axis,  cutting  a  cylindrical  or 
spiral  surface;    (2)    perpendicular-  to  the  axis,  as  in  cutting  the 
end  of  a  cylinder;  or  (3)  in  any  combination  of  the  two  directions 
named,  cutting  any  variety  of  surfaces  of  revolution.    The  cutting 
of  screw  threads  is  done  on  the  lathe. 


288 


MECHANICAL  PROCESSES 


Fig.  171  is  a  cut  selected  to  show  the  principal  features  of  a 
lathe  of  medium  size.  The  main  parts  are : 

AA.  Bed.  C.  Tail  stock. 

B.  Head  stock.  D.  Carriage. 

Work  is  suspended  between  the  centers  PP,  and  is  driven  by  a 
dog,  as  shown  in  Fig.  172;  or  both  centers  are  dispensed  with  and 
flat  work  is  secured  to  a  chuck  or  a  face  plate  screwed  on  the 
spindle-end  in  place  of  the  small  face-plate  F.  The  larger  face 
plate,  under  the  lathe,  is  marked  E. 


FIG.  171. — Engine  Lathe  of  Medium  Size. 

The  head  stock  carries  a  hollow  steel  spindle  on  which  are 
keyed  the  gear  wheel  S  which  drives  the  spindle,  and  the  small 
gear  wheel  K  which  drives  the  feed  and  screw-cutting  gear  at 
the  left  of  the  machine.  The  cone  wheels  G  and  their  small 
attached  gear  wheel  J  are  not  attached  to  the  spindle,  but  the 
cones  drive  the  spindle  either  directly  by  means  of  a  small 
sliding  bolt  which  attaches  them  to  the  wheel  S,  or  indirectly 
through  the  back  gear.  The  back  gear  consists  of  a  spindle  sup- 
ported on  the  head  stock  parallel  to  the  main  spindle,  on  one  end 
of  which  is  fixed  the  large  gear  wheel  II  and  on  the  other  end  is 
fixed  a  small  gear  wheel  not  visible.  The  wheels  of  the  back  gear 
may  be  thrown  in  or  out  of  gear  with  J  and  S  by  a  lever  L,  and 


THE  MACHINE  SHOP 


289 


when  they  are  in  gear,  the  bolt  connecting  the  cones  with  S  must 
be  dropped  out  of  its  driving  notch.  The  cone  G  is  driven  by  a 
belt  from  a  corresponding  cone  over  head.  The  back  gear  gives 
slower  speed  and  greater  power. 

The  tail  stock  carries  the  dead  center  which  may  be  moved 
forward  or  backward  by  the  hand  wheel  for  adjusting  it  to  hold 
work  in  the  lathe.  The  tail  stock  may  be  clamped  at  any  position 
along  the  bed.  For  supporting  a  bar  which  is  to  be  cut  tapered, 
the  dead  center  may  be  moved  perpendicular  to  the  length  of  the 
bed. 

A  tool  is  shown  clamped  in  the  tool  post  T.  Its  cutting  motions 
are  derived  from  the  leading  screw  M  or  from-  the  feed  rod  N. 


FIG.  172. 

The  leading  screw  is  used  in  cutting  threads.  Any  desired  combi- 
nation of  change  wheels  may  be  placed  in  gear  at  the  left  to  give 
any  desired  speed  to  the  tool  in  relation  to  the  speed  of  the  lathe. 

The  carriage  D  moves  along  the  shears  or  top  of  the  bed,  and 
the  various  attachments  on  the  apron  0  serve  to  facilitate  the 
quick  adjustment  and  to  regulate  the  various  motions  of  the  tool. 

The  compound  slide  rest,  consisting  of  the  two  parts  Q  and  R, 
carries  the  tool  post  and  governs  the  motions  of  the  tool  other  than 
in  the  direction  along  the  lathe  bed.  The  part  Q  travels  per- 
pendicular to  the  lathe  bed,  and  the  part  R  is  mounted  on  a 
vertical  pivot  in  Q  which  enables  its  slide  to  move  the  tool  in  a 
line  making  a  greater  or  less  angle  with  the  direction  of  motion 
of  the  part  Q. 


290 


MECHANICAL  PROCESSES 


The  term  back  lash  is  frequently  heard  in  speaking  of  machine 
tools,  and  particularly  of  lathe  gearing.  This  is  the  slack  motion 
noticed  when  reversing  a  train  of  gear  wheels,  due  to  the  loose 
fitting  between  the  teeth  of  wheels  which  mesh  together. 

319.  Varieties  of  the  Lathe. — Lathes  are  designated  according 
to  their  different  types.  Among  these  are  (1)  hand  lathes;  (2) 
machine  lathes;  (3)  gap  lathes,  and  (4)  turret  lathes. 

The  hand  lathe  was  mentioned  with  the  machinery  of  the  pattern 
shop.  This  lathe  is  frequently  made  small  enough  to  be  mounted 
on  a  bench  and  is  called  a  bench  lathe. 

The  machine  lathe,  a  type  contrasted  with  the  hand  lathe,  cuts 
metals  by  a  tool  fastened  on  the  lathe  carriage.  A  small  machine 
lathe  may  be  driven  by  foot  power  and  is  called  a  foot  lathe.  A 


FIG.  173.— Turret  of  a  Turret  Lathe. 

machine  lathe  is  designated  as  a  screw-cutting  lathe  when  it  is 
equipped  with  a  leading  screw  and  change  wheels  for  cutting 
threads. 

Many  small  lathes  have  no  live  centers  nor  tail  stocks.  A  chuck 
is  screwed  on  the  main  spindle  to  hold  a  rod  which  is  turned  to 
shape  as  in  the  screw-cutting  machine.  This  type  is  called  the 
chucking  lathe. 

Large  machine  lathes  are  built  to  run  at  suitable  speed  for  rapid 
cutting  made  possible  by  high-speed  steel,  and  are  designated  as 
high-speed  lathes,  confusing  them  with  small  lathes  run  at  high 
speed. 

A  very  important  modification  of  the  machine  lathe  is  the  gap 
lathe.  This  lathe  is  built  to  be  of  use  through  a  very  wide  range 
of  ordinary  work,  and  is  intended  for  a  shop  of  limited  equipment. 
It  differs  from  the  lathe  described  in  the  preceding  paragraph  by 


• 


THE  MACHINE  SHOP  291 

having  a  gap  in  the  bed  just  under  the  end  of  the  main  spindle  to 
provide  for  carrying  a  very  large  face  plate  which  holds  flat  work 
of  large  diameter.  The  lathe  bed  is  very  deep  and  is  made  in 
two  sections  divided  horizontally.  The  upper  section,  which  carries 
the  carriage  and  the  tail  stock,  may  be  slid  along  the  lower  part  of 
the  bed  to  open  the  gap  under  the  edge  of  the  face  plate. 

The  feature  of  the  turret  or  monitor  lathe  is  shown  in  Fig.  173. 
The  tail  stock  is  displaced  by  a  turret  T  which  carries  several 
tools  which  are  used  in  consecutive  order  on  the  piece  of  work 
held  in  the  chuck  C.  The  turret  is  mounted  on  a  vertical  spindle 


FIG.  174. — Lathe  Tools. 

on  the  slide  8.    This  slide  is  moved  to  carry  the  tools  into  contact 
with  or  away  from  the  work  by  the  long  hand-bars. 
This  lathe  saves  much  time  in  changing  tools. 
320.  Lathe  Tools. — Fig.  174  shows  the  different  shapes  of  tools 
ordinarily  used  in  lathe  work.     These  are  made  of  high-carbon 
steel,  or  preferably  of  self-hardening  alloy  steel  for  heavy  work. 
The   cutting  ends   are  forged,   hardened,   tempered   and   ground. 
They  are  designated  as  follows : 

(1-2)   Left  and  right-hand  side-tools. 

(3-7)   Bent  and  straight  cut-off  tools. 

(4-5)   Right  and  left-hand  diamond  points. 

(6)   Fillet  or  round-nose  tool. 

(8)   Threading  tool. 


892  MECHANICAL  PROCESSES 

(9)  Bent  threading  tool. 

(10)  Koughing  tool. 

(11)  Inside  boring  tool. 

(12)  Inside  threading  tool. 

The  diamond-point  tools,  Xos.  4  and  5,  are  about  superseded 
by  a  round-nosed  tool  shown  in  Fig.  175  which  is  superior  for 
size  of  chip,  resistance  to  wear,  and  smoothness  of  cut,  particularly 
on  heavy  work.  This  tool  shows  its  advantages  best  when  made 
of  high-speed  steel. 

Because  of  the  high  cost  of  alloy  steels  used  for  tools,  much  ex- 
pense is  saved  by  having  merely  a  cutting  end  of  alloy  steel  held 
in  a  tool  holder.  These  holders  are  in  many  styles  to  suit  the 
shape  of  the  cutting  end. 


FIG.  175. — Round-Nose  Tool. 

Many  special  tools  are  devised  for  use  in  turret  lathes,  as  these 
lathes  do  special  work  and  do  not  use  the  ordinary  lathe  tools. 

321.  Lathe  Attachments. — Several  attachments  are  provided  to 
enable  a  lathe  to  be  used  for  various  kinds  of  work.     The  most 
important  among  these  are  the  face  plate,  cliuck,  mandrel ,  boring 
~bar  and  steady  rest.    There  are  other  attachments,  as  taper  attach- 
ment,  center-grinding   attachments,   etc.,  which   are   very   useful, 
but  need  not  be  described  here. 

A  face  plate  is  shown  at  E  in  Fig.  171.  It  screws  on  the  end  of 
the  main  spindle  in  place  of  the  small  face-plate  F.  "Work  which 
cannot  be  suspended  between  centers  is  clamped  by  means  of  bolts 
and  iron  clips  to  the  face  plate. 

322.  The  Lathe  Chuck. — Oftentimes  work  can  neither  be  sus- 
pended between  centers  nor  bolted  to  the  face  plate.     In  this  case 
it  is  held  by  a  chuck,  a  type  of  which  is  shown  in  Fig.  176.    The 
four  jaws  (one  of  which  is  marked  B)  may  be  adjusted  in  a  radial 
direction  by  a  wrench  on  one  of  the  nuts  (7.    This  nut  is  the  end  of 
a  radial  screw.     The  jaws  grip  the  work  by  clamping  down  on  it 
fcr  by.  pressing  out  against  the  inside  of  hollow  work  of  large 


THE  MACHINE  SHOP 


293 


diameter.     The  jaws  may  be  turned  end  for  end  to  secure  work  in 
the  two  ways  just  designated. 

Chucks  have  usually  three  jaws  or  four  jaws,  and  they  are 
classed  as  independent  or  universal.  The  jaws  of  an  independent 
chuck  are  moved  separately  by  the  wrench,  while  the  jaws  of  the 


FIG.  176. — Lathe  Chuck. 

universal  chuck  have  their  controlling  screws  so  connected  by  an 
internal  mechanism  as  to  make  then  move  outward  or  inward  to- 
gether. Many  chucks  are  made  to  be  changed  by  a  clamp  and 
screw  from  universal  to  independent  and  vice  versa.  Chuck  jaws 
may  be  fitted  to  slotted  face  plates. 


FIG.  177. — Work  Mounted  on  Lathe  Mandrel. 

323.  Lathe  Mandrels. — There  are  many  pieces  of  lathe  work 
which  are  pierced  with  a  cylindrical  hole  and  which  can  be  mounted 
on  a  bar  suspended  between  lathe  centers.  Fig.  177  shows  an 
arrangement  of  this  kind.  The  bar  B  is  called  a  mandrel.  It 


294  MECHANICAL  PUOCESSES 

has  a  very  slight  taper  and  rnu.st  fit  the  work  very  closely,  in  fact 
it  is  driven  into  the  work  by  means  of  a  copper  maul.  Such  an 
arrangement  enables  both  sides  of  the  work  to  be  readily  machined. 
When  the  work  is  finished,  the  mandrel  is  driven  out. 

Mandrels  are  so  frequently  used  in  the  machine  shop,  and  they 
must  fit  the  work  so  neatly  that  several  forms  of  expanding 
mandrels  have  been  devised  so  that  one  mandrel  may  suffice  for 
holo  varying  within  a  range  of  about  5  per  cent  in  diameter.  Fig. 
178  shows  a  useful  type  of  expanding  mandrel  which  may  easily 
be  made  in  the  shop.  It  consists  of  a  sleeve  or  bushing  7?  and  a 
mandrel  M.  The  mandrel  is  usually  about  8  or  10  inches  long, 
centered  for  suspending  between  the  latin-  centers,  threaded  at  one 


FIG.  178. — Expanding  Mandrel. 

end  for  a  nut,  and  (ape-red  for  a  dislanee  of  .".  or  1  inches  from  the 
threaded  end  so  that  the  largest  diameter  of  the  tapered  part  is 
about  ."i  per  eent  more  than  tin-  smallest  diameter.  The  bushing  i- 
n-aim-d  in.-idi-  to  the  taper  of  (he  mandrel,  is  turned  cylindrical 
oiif-ide,  has  a  number  of  slits  cut  along  its  outer  surface  nearly 
through  (he  metal,  and  has  one  slit  cut  entirely  through.  The 
bushing  is  slipped,  large  end  first,  over  the  threaded  end  of  the 
mandrel  and  is  pushed  along  by  aid  of  the  nut  until  the  taper 
expands  it  ou(  firmly  against  the  work  it  is  intended  to  fit. 

324.  The  Boring  Bar. — K<>r  boring  ou(  hollow  cylindrical  work 
on  (he  lathe,  it  is  usually  secured  to  the  face  plate  as  shown  in 
Fig.  IT'JJ.  If  the  work  does  ti'.i  extend  more  than  (1  or  S  inches 
from  the  face  plate,  it  may  be  hmvd  by  tin-  in>ide  hoi-ing  tool. 


THE 


300 


For  longer  work,  a  bar  B  is  suspended  between  lathe  centers. 
This  bar  carries  a  cutter  head  C  to  which  is  clamped  two  or  more 
cutting  tools  as  shown.  The  cutter  head  is  fed  along  the  bar  by 
the  handle  Hf  which  is  pushed  by  the  travel  of  the  lathe  carriage. 


17&—  Boring  Bar, 


The  key  Kf  traveling  in  a  slot  in  the  bar,  keeps  the  cutter  head 
from  revolving, 

Another  form  of  boring  bar  is  shown  in  Fig,  ISO,  The  too! 
glide  is  removed  from  the  lathe  and  the  cylindrical  work  is  matured 
on  the  lathe  carriage.  The  rigid  bar,  carrying  the  steel  cutter  A, 
is  suspended  between  centers,  and  as  the  bar  rewires,  the  work  is 


F*c,  m.—  Borfcas 


mored  slowly  along  by  the  carriage.    The  pin  B  keep?  the  cutter 
firmly  in  place, 

**  are  several  other  types  of  the  boring  bar,  bnt  boring  is  a 
work  not  usually  done  on  a  lathe  except  in  a  stoop  of  limited  equip- 

. 


296 


MECHANICAL  PROCESSES 


325.  The  Steady  Rest. — When  a  long  piece  of  work  is  suspended 
between  lathe  centers  it  will  sag  more  or  less.  Also  very  heavy 
work  is  too  heavy  for  safe  support  by  the  lathe  centers  and  addi- 
tional support  must  be  provided.  To  prevent  sagging  and  provide 
increased  support  for  work,  a  steady  rest,  as  shown  in  Fig.  181, 
is  used.  The  principle  of  this  may  be  provided  in  simpler  form, 
such  as  blocking  up  under  the  work  and  making  a  bearing  on  wood, 
or  metal  kept  lubricated. 

The  steady  rest  here  shown  is  clamped  on  the  bed  of  the  lathe 
by  the  yoke  and  bolt  at  the  bottom,  and  the  three  sliding  pieces  are 


FIG.   181.— Steady  Rest. 

adjusted  by  the  long  screws  to  support  the  work  at  three  different 
points.  When  work  is  to  be  removed  from  the  lathe,  the  upper 
part  of  the  steady  rest  may  be  opened  on  its  hinge. 

326.  Centering  Work  for  the  Lathe. — Lathe  centers  must  be 
accurately  pointed  to  an  angle  of  60°.  They  must  be  kept  sharp- 
pointed,  smooth,  and  absolutely  free  from  grit  or  metal  chips. 

A  bar  to  be  suspended  in  the  lathe  must  be  centered  as  shown  in 
Fig.  177.  The  center  of  each  of  the  round  ends  of  the  bar  is 
located  by  means  of  dividers  or  otherwise,  marked  with  a  center 
punch,  drilled  to  a  depth  of  about  half  an  inch  or  more,  and 
countersunk  to  fit  the  taper  of  the  lathe  center.  The  end  may  be 


THE  MACHINE  SHOP  297 

recessed  to  insure  protection  to  the  countersunk  edge.  It  is  highly 
essential  that  this  center  be  kept  free  from  grit  or  chips,  burrs  of 
metal,  and  it  must  be  well  oiled. 

337.  Cutting  of  Screw  Threads. — A  screw  thread  is  a  helical 
groove  cut  on  an  internal  or  an  external  cylindrical  surface.  The 
cutting  of  threads  is  best  and  cheapest  done  by  machine.  Bolts 
and  nuts  are  usually  cut  by  dies  and  taps  held  in  machines  for  that 
kind  of  work  exclusively.  The  lathe  and  the  milling  machine  are 
employed  to  cut  threads  which  must  be  exact  in  form. 


FIG.  182. 

The  method  of  cutting  a  thread  in  the  lathe  is  as  follows :  The 
piece  to  be  threaded  is  centered  and  suspended  between  the  lathe 
centers  as  shown  in  Fig.  182.  A  center  gage  C  is  placed  against 
the  work  for  adjusting  the  threading  tool  T  on  the  lathe  carriage. 
The  notches  in  the  center  gage  are  angles  of  60°  and  are  so  cut 
that  a  line  bisecting  the  angle  is  perpendicular  or  parallel,  as  the 
case  may  be,  to  the  two  graduated  edges  of  the  gage.  The  cutting 
end  of  the  threading  tool  has  been  ground  to  a  60°  point,  as  tested 
by  the  gage  notch,  and  the  adjusting  of  the  tool  as  shown  insures 
the  symmetry  of  the  thread  surfaces. 


298  MECHANICAL  PROCESSES 

Change  wheels  are  placed  on  the  spindles  and  on  the  leading  screw 
at  the  end  of  the  lathe  to  make  the  requisite  combination  for 
moving  the  lathe  carriage  a  definite  distance  along  the  bed  for 
each  revolution  of  the  work.  When  the  machinist  sets  the  lathe  in 
motion  and  adjusts  the  tool  point  against  the  work,  a  groove  is 
cut  along  the  surface  of  the  cylinder  and  is  gradually  cut  deeper 
by  a  number  of  traverses  of  the  tool  until  the  required  depth  is 
attained. 

When  the  tool  reaches  the  end  of  each  cut,  it  is  quickly  drawn 
away,  the  lathe  is  reversed  to  carry  the  tool  back  to  the  starting 
point,  and  is  again  reversed  to  begin  a  new  cut. 


FIG.  183. 

328.  Forms  of  Threads.  Definitions. — A  screw  thread  may  be 
conceived  as  formed  on  a  cylinder  by  winding  thereon  a  piece  of 
triangular  wire,  as  shown  in  Fig.  183.  N  is  a  nut,  threaded  inside 
to  turn  on  the  screw. 

If  the  wire  is  wound  as  shown  on  the  end  B,  the  thread  is  right 
handed,  if  wound  in  the  reverse  direction,  as  on  the  end  D,  the 
thread  is  left  handed.  A  right-handed  thread  is  one  on  which  a 
nut  is  screwed  by  turning  the  nut  in  the  direction  of  the  hands  of 
a  watch  when  the  bolt  end  is  pointed  toward  the  operator. 

The  distance  between  two  adjacent  ridges  of  the  thread,  as  CC, 
is  the  pitch  of  the  screw. 

If  two  triangular  wires  (of  the  same  size)  are  wound  side  by 
side  on  the  cylinder  the  thread  is  a  double  thread.  The  pitch  re- 


THE  MACHINE  SHOP 


299 


mains  the  same,  but  a  nut  turned  one  turn  on  the  double  thread 
will  advance  twice  the  pitch.  The  distance  which  the  nut  advances 
in  one  turn  is  called  the  lead  of  a  screw,  and  it  will  be  seen  that  in 
this  case  the  lead  is  twice  the  pitch. 

The  form  of  a  thread  is  the  profile  it  shows  in  a  section  made  by 
a  plane  passing  through  the  axis  of  the  cylinder  on  which  the 
threads  are  cut.  The  form  most  used  is  the  V  thread,  and  other 


I-/H 

1    -y/fo*i 


fits/tress 


Acme 
FIG.  184. — Forms  of  Threads. 


forms  used  for  special  purposes  are  the  square  thread,  the  Acme  or 
worm  thread,  and  the  buttress  or  trapezoidal  thread.  These  forms 
are  shown  in  Fig.  184. 

329.  Standard  Threads. — The  unlimited  forms  of  threads  which 
may  be  used  has  brought  about  efforts  to  standardize  the  form  and 
pitch  of  the  V  thread.  The  efforts  have  resulted  in  the  U.  S. 


FIG.  185. 


FIG.  186. 


standard  for  the  United  States,  the  Whitworth  standard  for  Eng- 
land, and  the  metric  or  international  standard  for  Continental 
Europe. 

The  form  of  the  U.  S.  standard  is  shown  in  Fig.  185. 

The  form  of  the  Whitworth  standard  is  shown  in  Fig.  18G. 

The  pitch  of  threads  is  standardized  by  designating  a  definite 
pitch  for  threads  cut  on  a  cylinder  of  specified  diameter;  i.  c.,  a 


300  MECHANICAL  PROCESSES 


bolt  i/^-inch  diameter  has  13  threads  per  inch,  and  a  bolt  of  1-inch 
diameter  has  8  threads  per  inch  by  the  U.  S.  standard. 

Small  threads  may  be  cut  on  the  lathe  by  the  hand  chasers 
shown  in  Fig.  187,  though  these  are  more  conveniently  used  for 
cutting  out  to  a  greater  depth  a  thread  which  was  not  cut  deep 
enough. 

Thread  gages  for  measuring  the  pitch  of  threads  are  among  the 
small  tools  for  machine  shop  use. 

330.  Drilling  Machines.  —  The  cutting  of  cylindrical  holes  of 
greater  or  less  size  in  metals  is  a  very  varied  requirement  in 
machine-shop  practice  and  many  methods  are  employed  for  ac- 
complishing this  work,  depending  upon  the  diameter  and  length  of 
the  hole.  Small  holes  are  drilled  on  the  drilling  machine,  very 
long  holes,  as  in  gun  barrels  or  propeller  shafting,  are  drilled  in 


Jns/cfe 


FIG.  m.— Hand  Chasers. 

the  boring  lathe,  and  cylindrical  holes  of  large  diameter,  as  in  a 
steam  cylinder,  are  bored  on  the  boring  mill.  Usually  a  hole  is 
cast  in  a  casting  to  reduce  to  a  minimum  the  work  of  boring,  and 
in  a  less  degree  forgings  are  made  hollow,  when  so  required,  for 
the  same  purpose.  Generally  the  term  drilling  is  applied  to  the 
cutting  of  small  holes  by  a  drill,  and  boring  is  applied  to  the  cut- 
ting of  larger  holes  which  may  or  may  not  have  been  previously 
made  in  casting  or  forgings. 

There  are  many  different  styles  of  drilling  machines.  The 
principal  styles  among  these  are  (1)  the  vertical  drill;  (2)  the 
radial  drill;  (3)  the  gang  drill,  and  (4)  the  multiple  spindle 
drill.  There  are  many  sizes  of  each  of  these  styles  designed  for 
particular  kinds  of  work. 

331.  The  Vertical  Drill. — Fig.  188  shows  a  vertical  drilling 
machine  of  a  type  much  used.  The  drill  is  carried  in  a  socket  in 
the  lower  end  of  the  vertical  spindle  VV.  The  spindle  is  made  to 


THE  MACHINE  SHOP 


301 


revolve  by  a  belt  on  the  cones  CC,  and  is  fed  gradually  downward 
either  by  the  power-feed  mechanism  driven  by  a  belt  over  the  small 
cones  SS,  or  by  the  hand  lever  L  which  may  be  swung  down  hori- 
zontally for  convenient  handling.  Both  power  and  hand  feeds 
may  be  readily  thrown  out  of  gear  when  the  spindle  is  to  be 


FIG.  188.— Vertical  Drill. 

quickly  raised  or  lowered  by  the  hand  wheel  H.     The  spindle 
moves  up  and  down  in  a  vertical  direction. 

Work  to  be  drilled  rests  ofi  the  table  T,  or  may  rest  on  the  base 
F.  The  faces  of  both  the  table  and  the  base  are  horizontal,  hence 
are  always  perpendicular  to  the  direction  of  travel  of  the  drill. 
The  table  may  be  adjusted  vertically  or  swung  horizontally  as 
desired. 
20 


302 


MECHANICAL  PROCESSES 


A  shop  usually  has  a  small  vertical  drill  fed  only  by  hand  and 
used  for  drilling  holes  of  i/4-inch  diameter  or  less.  This  is  known 
as  a  sensitive  drill. 

Gang  drills  and  multiple  spindle  drills  have  several  spindles  and 
drill  several  holes  at  the  same  time. 


FIG.  189.— Full-Universal  Radial  Drill. 

332.  The  Radial  Drill. — The  changing  of  position  of  work  on  a 
machine  consumes  time  which  may  add  considerably  to  the  expense 
of  large  work.  The  radial  drill  is  so  designed  that  when  a  piece 
of  work  is  secured  to  the  drill  table,  which  is  placed  on  a  solid 
foundation  for  holding  very  heavy  work,  the  drill  spindle  may  be 
placed  over  any  part  of  the  work  without  moving  the  latter. 


THE  MACHINE  SHOP 


303 


There  are  three  classes  of  radial  drills,  viz.,  (1)  the  plain  radial 
drill,  in  which  the  drill  spindle  is  always  vertical,  but  may  not  be 
swung  over  any  point  of  the  work;  (2)  the  half-universal  drill 
in  which  the  spindle  may  be  swung  over  any  point  of  the  work  and 
in  addition  may  swing  in  one  plane  at  any  angle  to  the  vertical  up 


FIG.  190. 

to  complete  reversal  of  the  direction  of  the  drill,  and  (3)  the  full- 
universal  drill  in  which  the  spindle  may  be  swung  in  any  plane  at 
any  angle  to  the  vertical.  Fig.  189  shows  a  universal  radial  drill 
the  drill  spindle  of  which  may  be  moved  to  any  position  within  the 
reach  of  the  machine  and  placed  at  any  angle  desired. 

333.  Drills  and  Attachments  for  Drilling  Machines.— Fig.  190 
shows  three  twist  drills  and  a  countersink  which  are  much  used 


FIG.  191.— Drill  Chuck. 

with  drilling  machines.  Drill  C  is  made  of  a  twisted  bar  of  high- 
speed steel.  Drills  A  and  C  have  taper  shanks.  They  are  placed 
in  a  taper  socket  and  the  socket  is  placed  in  the  end  of  the  drill 
spindle.  Drill  B  and  the  countersink  have  straight  shanks.  They 
are  held  in  a  small  chuck  shown  in  Fig.  191.  Small  drills  have 


304  MECHANICAL  PROCESSES 

straight  shanks.  The  countersink  is  used  for  reaming  the  end  of 
a  hole  to  the  shape  of  a  lathe  center. 

A  vise,,  of  which  Fig.  193  is  one  type,  is  necessary  for  holding 
small  work  accurately  on  the  drill  table. 

When  the  drilling  of  holes  in  duplicate  pieces  of  work  is  repeated 
many  times,  a  jig  is  made  with  the  holes  drilled  through  it  in 
correct  position  and  this  is  used  as  a  guide  for  drilling  by  placing 
it  over  the  work  and  thereby  avoiding  the  necessity  of  marking  the 
holes  on  each  piece.  Work  of  this  kind  is  quickest  done  on  a 
multiple  spindle  drill.  Jigs  in  simplest  form  are  made  from  plates 
of  cast  iron  or  rolled  steel.  Many  forms  of  jigs,  however,  are  very 
elaborate,  consisting  of  cast-iron  boxes  with  guide  holes  drilled 
through  the  sides  at  the  desired  angles  and  protected  by  bushings. 
A  piece  of  work  to  be  drilled  is  placed  in  one  of  these  box  jigs  and 
secured  in  a  particular  position  to  insure  drilling  similar  holes  alike 
in  every  piece. 

334.  The  Planer. — This  machine  is  used  to  cut  plane  surfaces 
or  straight  grooves.  Fig.  192  shows  a  type  of  planer  much  used. 
Work  is  secured  usually  by  bolts  and  clips  to  the  heavy  table  T, 
the  surface  of  which  is  level.  This  table  is  made  to  move,  by 
mechanism  under  the  machine,  back  and  forth  along  two  level 
Y-shaped  grooves  B  in  the  planer  bed.  The  distance  of  travel  of 
the  table  is  governed  by  two  adjustable  stops  EE  which  strike  a 
lug  of  the  reversing  mechanism  on  the  side  of  the  planer  bed  and 
cause  the  two  driving  belts  to  shift  on  the  pulleys  GrG.  One  of 
these  belts  is  open  and  the  other  is  crossed  to  drive  the  pulley  in 
opposite  directions.  The  middle  wheel  runs  idly  and  merely 
facilitates  the  shifting  of  the  belts. 

All  that  part  of  the  machine  above  the  table  is  designed  for 
holding  the  tool  rigidly  and  for  controlling  its  horizontal  and 
vertical  adjustment.  The  housings  HH  carry  the  cross-rail  C 
which  may  be  raised  or  lowered  by  the  hand  mechanism  above  the 
machine.  The  head  D  slides  horizontally  along  the  cross  rail,  and 
its  parts  are  arranged  for  raising  or  lowering  the  tool,  and  for 
setting  to  tool  at  an  angle  to  make  cuts  along  the  sides  of  a  piece 
of  work. 

The  tool  is  clamped  by  four  bolts  to  the  apron  A,  and  it  makes 
a  cut  only  when  the  table  travels  to  the  right  in  the  view  here 


THE  MACHINE  SHOP 


305 


shown.  When  the  work  travels  back  to  the  left,  a  horizontal  bolt 
J  which  hinges  the  upper  edge  of  the  apron  A  allows  the  tool  to 
swing  out  of  the  way  as  it  drags  over  the  work.  The  tool  may  be 
gradually  fed  horizontally  across  the  table  or  may  be  fed  vertically. 
The  feeding  mechanism  is  marked  KLPRS.  This  mechanism 
moves  the  tool  after  it  has  finished  its  cut  and  when  the  machine 
is  reversing.  When  a  series  cuts  is  finished  across  a  piece  of  work, 
the  tool  point  is  lowered  slightly  by  the  handle  N  for  another 
series. 


FIG.  192. — Planer. 

The  driving  mechanism  of  the  planer  table  is  designed  to  give 
the  table  a  quicker  motion  for  the  return  than  for  the  cutting 
stroke.  This  is  known  as  the  quick  return  motion. 

335.  Types  of  the  Planer. — For  very  heavy  work  of  considerable 
bulk,  an  open-sided  planer  is  used.  This  is  somewhat  similar  to 
the  planer  just  described,  except  that  one  of  the  housings  is 
omitted. 

Another  type  of  planer  designed  for  planing  off  the  end  of  a 
large  forging,  too  long  to*  rest  cross-wise  of  the  planer  bed,  is  the 


306  MECHANICAL  PROCESSES 

rotary  planer.  The  work  is  secured  to  a  fixed  base  plate,  and  the 
end  is  presented  to  the  face  of  a  heavy  revolving  disc  which  carries 
many  cutting  tools.  As  the  disc  revolves,  the  tools  cut  the  end 
of  the  work,  which  is  fed  in  a  direction  parallel  to  the  face  of  the 
disc. 

336.  Planer  Tools. — As   in  the  case   of  lathe  tools,   these  are 
made   of   rectangular   steel   bar   material,   forged,   hardened,   and 
ground  to  shape.     The  planer  has  fewer  regular  tools  than  the 
lathe.     There  is  no  threading  tool  for  the  planer,  but  the  round 
nose  and  side  tools  are  very  similar  for  lathe  and  planer.    A  square- 
nose  finishing  tool  is  much  used  with  the  planer. 

337.  The  Planer  Chuck  and  Planer  Jack. — The  chuck  or  vise 
shown  in  Fig.  193  is  very  useful  for  planer  and  shaper  work.    It  is 


FIG.  193. — Planer  Chuck.  FIG.  194. — Planer  Jack. 

bolted  to  the  table  and  used  to  hold  small  work  in  exact  position 
for  accurate  cutting. 

In  the  careful  adjusting  of  heavy  work  on  the  planer  table  to 
the  position  desired  for  planing,  small  jacks  such  as  shown  in  Fig. 
194  are  used.  These  are  of  various  heights,  from  about  1%  to  6 
inches  or  more.  They  may  be  left  under  the  work,  but  it  is  best  to 
replace  them  with  wedges  of  wood  or  iron,  on  which  the  work  rests. 

338.  The  Planing  of  Propeller  Blades. — The  driving  surface  of 
a  propeller  blade  is  made  up  of  straight  line  elements  radiating 
from  the  axis  of  the  propeller.  This  fact  enables  a  true  and  smooth 
surface  to  be  machined  on  the  blade  by  means  of  the  planer.  The 
driving  surface  of  the  blade  is  generated  by  a  straight  line  mov- 
ing at  a  uniform  rate  along  the  axis  of  the  propeller  and  at  the 
same  time  revolving  about  this  axis  at  a  uniform  angular  rate. 


THE  MACHINE  SHOP 


307 


A  device  has  been  perfected  which  rests  on  the  planer  table  and 
holds  a  single  blade  in  such  position  that  an  element  of  the 
blade  is  parallel  to  the  direction  of  motion  of  the  table.  This 
device  has  a  feeding  arrangement  which  gives  the  blade  such  a 
combined  motion  of  translation  and  revolution  that  each  of  its 
elements  in  succession  is  brought  into  a  position  which  the  too1 
will  follow  as  the  table  moves. 

In  the  foundry,  a  propeller-blade  mould  is  swept  up  in  loam  by 
a  sweep,  the  edge  of  which  is  raised  and  revolved  at  the  same  time 
to  generate  the  driving  surface  of  the  blade. 


FIG.  195. — Shaper. 

339,  The  Shaper. — This  is  virtually  a  planer  for  planing  small 
work.  It  is  not  designed  like  the  planer,  however,  and  the  essen- 
tial difference  is  that  the  work  table  remains  stationary,  except 
for  the  feeding  motion,  and  the  tool  is  moved  back  and  forth  over 
the  work.  The  shaper  is  a  quicker-moving  machine  than  the 
planer.  It  cuts  in  but  one  direction  of  its  stroke. 

Fig.  195  shows  a  type  of  small  shaper  much  used.  A  feature  of 
all  simpers  is  the  quick-return  motion,  as  mentioned  for  the  planer. 


308 


MECHANICAL  PROCESSES 


The    Whitworth    quick-return    motion    is    much    used    in    shaper 
mechanism. 

Work  is  clamped  in  the  vise  V  which  is  bolted  to  the  table  T. 
The  table  is  carried  by  the  cross-rail  R  which  may  be  raised  or 
lowered  by  hand  mechanism  along  its  slide  S  at  the  front  of  the 
column  of  the  machine.  An  adjustable  support  B  assists  to  hold 
the  table  rigidly. 


FIG.  196. — Plain  Milling  Machine. 

The  tool,  which  is  not  unlike  a  lathe  tool  in  form,  is  clamped 
in  the  tool  post  P  which  is  carried  by  an  apron  on  the  head  H. 
This  head  is  carried  by  the  ram  M  which  is  made  to  slide  back  and 
forth  in  its  guides  on  the  top  of  the  machine.  The  vertical  position 
of  the  tool  is  adjusted  by  the  screw  handle  C.  The  length  of  travel 
of  the  ram  is  adjusted  to  suit  the  work  by  a  hand  crank  on  the 
spindle  D,  and  the  range  of  its  travel,  i.  e.,  the  limits  of  the  ends 
of  its  stroke,  is  governed  by  the  crank  above  the  ram. 


THE  MACHINE  SHOP  309 

The  machine  is  driven  by  means  of  a  belt  on  one  of  the  cone 
wheels.  As  the  rani  moves  back  and  forth,  the  table  is  gradually 
fed  at  the  end  of  each  stroke  along  the  cross  rail  by  the  mechanism 
KLN  until  the  work  is  carried  entirely  across  the  range  of  travel 
of  the  tool.  The  tool  is  then  slightly  lowered  by  the  screw  handle 
for  a  new  cut,  and  the  table  is  fed  back  in  the  opposite  direction. 

The  machine  is  so  built  that  the  ram  and  table  move  hori- 
zontally, one  at  right  angles  to  the  other,  and  the  cross  rail  raises 
or  lowers  vertically. 

For  holding  small  flat  work  of  steel  or  iron  quickly  and  readily, 
a  small  electro-magnetic  chuck  has  been  designed  for  use  with  the 
shaper.  It  is  bolted  to  the  table  or  clamped  in  the  vise  and  is 
supplied  with  direct  current  for  the  magnets. 

340.  The  Milling  Machine. — This  machine  is  shown  in  simple 
form  in  Fig.  196.     Milling  machines  are  used  for  both  plain  and 
intricate  cutting  of  great  variety.     They  are  adopted  to  that  kind 
of  cutting  which  is  of  particular  or  peculiar  contour,  which  must 
be  in  particular  relative  position  to  other  cutting  on  a  piece  of 
work,  and  which  must  be  accurate  to  a  high  degree. 

Milling  machines  are  employed  mostly  on  small  work,  yet  some 
machines  are  built  for  large  and  heavy  work. 

The  teeth  of  plain  and  helical  gear  wheels,  the  spiral  grooves 
in  a  twist  drill,  the  longitudinal  grooves  in  taps  and  in  many 
forms  of  milling-machine  cutters,  slots  and  key-ways  in  shafts, 
screw  threads  of  long  pitch,  and  hexagon  nuts  or  other  pris- 
matic work  may  be  mentioned  as  examples  of  milling-machine 
cutting.  A  milling  machine  may  be  used  for  such  cutting  as  is 
done  on  a  small  lathe,  shaper,  drill,  boring  machine  and  slotting 
machine,  or  for  any  combination  of  the  kinds  of  cutting  done  by 
any  of  these  machines.  With  the  several  attachments  now  de- 
signed for  the  modern  milling  machine,  it  can  do,  within  the 
limits  of  size  of  its  work-table,  the  work  of  any  other  machine 
tool  in  the  shop,  and  even  more. 

341.  Description  of  the  Milling  Machine. — Work  is  held  in  a 
vise  or  other  attachment  which  is  bolted  to  the  slots  of  the  table 
(Fig.  196).     Wheel-shaped  cutters  placed  on  the  arbor  are  made 
to  revolve  by  means  of  the  main  spindle  which  is  hollow,  and  on 


310  MECHANICAL  PROCESSES 

which  is  keyed  the  driving  cone.  The  outer  end  of  the  arbor  is 
supported  by  the  adjustable  over-arm.  The  cones  are  driven  by  a 
belt  from  similar  cones  overhead. 

After  work  is  secured  on  the  machine  and  cutters  are  placed  on 
the  arbor,  the  table  is  adjusted  by  hand  mechanism  to  bring  the 
work  in  range  of  the  cutters.  The  table  may  be  raised  or  lowered 
by  the  elevating  screw  which  controls  the  vertical-sliding  knee, 
and  it  may  be  adjusted  horizontally  toward  or  from  the  body  of 
the  machine  by  moving  the  saddle  which,  in  the  plain  machine, 
slides  back  and  forth  in  but  one  horizontal  direction  on  the  knee. 
The  table,  the  saddle  and  the  knee  are  adjusted  by  means  of  the 
four  cranks  shown. 

When  the  machine  is  in  operation,  with  the  work  adjusted  for 
cutting,  the  table  is  fed  horizontally  along  the  saddle  in  either 
direction  perpendicular  to  the  axis  of  the  arbor,  by  means  of  the 
feed  shaft  and  its  mechanism.  The  reverse  lever  determines  the 
direction  of  travel  of  the  table,  and  the  trip  dogs  are  adjusted  to 
stop  the  table  within  certain  limits  of  travel  as  they  come  into 
contact  with  the  trip  plunger.  The  feed-trip  lever  is  used  to  stop 
the  feed  instantly  by  hand.  The  whole  feed  mechanism  is  driven 
by  a  belt  on  the  feed  cones. 

Some  forms  of  cutters,  which  reach  into  grooves  or  slots  in  a 
piece  of  work,  have  their  own  shanks  which  fit  into  a  socket  or 
collet  similar  to  a  drill  shank.  This  collet  fits  into  the  end  of 
the  spindle.  When  these  cutters  are  used,  neither  the  arbor  nor  the 
over-arm  are  used. 

342.  The  Universal  Milling  Machine. — The  machine  in  Fig.  196 
is  known  as  a,  plain  milling  machine  because  its  table  cannot  turn 
on  the  saddle.  The  machine  in  Fig.  197  is  a  universal  milling 
machine,  as  its  saddle  is  made  in  two  parts,  divided  horizontally 
at  H  and  so  adjusted  that  the  upper  part  may  revolve  on  a  vertical 
spindle  on  the  lower  part,  allowing  the  table  to  be  turned  to  a 
considerable  angle  from  its  position  as  shown  in  the  plain  machine. 
The  junction  of  the  two  parts  of  the  saddle  is  marked  by  a  gradu- 
ated circle  so  that  the  angle  through  which  the  table  is  moved  can 
be  readily  measured. 


THE  MACHINE  SHOP 


311 


The  parts  of  the  machine  (similarly  named  to  those  of  the  plain 
machine)  are  as  follows: 

S.  Spindle.  B.  Elevating  screw. 

C.  Driving  cone.  //.  Saddle. 

F.  Back  gear.  TT.  Work  table. 


FIG.  197. — Universal  Milling  Machine. 


A.    Arbor. 

N.  Arbor  support. 

GG.  Over-arm. 

MM.  Over-arm  brace. 

D.  Brace  clamp. 

KK.  Knee. 


EE.  Trip  dogs. 
L.  Feed  shaft. 
J.  Reverse  lever. 
TV.  Dividing  head. 
X.  Foot  stock. 


318 


MECHANICAL  PROCESSES 


The  dividing  head  and  foot  stock  correspond  to  the  head  and  tail 
stocks  of  a  lathe.  The  dividing  head  is  used  in  cutting  gear 
wheels,  sides  of  prisms,  and  similar  work  which  must  be  divided 
into  an  exact  number  of  parts  around  its  periphery,  as  shown  in 


THE  HENDEY  MACHINE  CO, 

TORRINGTON,  CONN. 


FIG.  198. — Example  of  Milling-Machine  Cutting. 

Fig.  198.  Divisions  are  regulated  by  the  dividing  wheel  R.  When 
work  suspended  on  the  centers  of  the  dividing  head  and  the  foot 
stock  must  be  given  a  motion  of  revolution  as  part  of  the  operation 
of  milling  it,  the  gear  wheels  Q  (Fig.  197)  are  connected  to  the 
feeding  mechanism  of  the  machine.  For  cutting  spiral  grooves 
and  coarse  threads,  the  work  is  revolved  on  these  centers  and  at 


THE  MACHINE  SHOP  313 

the  same  time  is  given  a  motion  of  translation  by  the  movement  of 
the  table. 

343.  Milling-Machine  Cutters  and  Arbors. — Fig.  199  shows  a 
group  of  cutters,  arbors  and  collets. 

Cutters  are  made  of  higli-speed  steel  for  roughing  cuts  and  of 
carbon  steel  for  lighter  or  finishing  cuts.  After  a  cutter  is 
hardened  for  cutting  it  is  ground  to  exact  shape  in  a  special 
machine  made  for  accurate  grinding.  In  this  way  all  the  teeth 
of  a  cutter  are  made  to  cut  in  the  same  path. 

344.  Milling-Machine     Attachments. — The    usual     milling-ma- 
chine attachments  are  the  vise  and  the  dividing  head,  both  for 
holding  work. 


FIG.  199. — Milling-Machine  Cutters,  Arbors  and  Collets. 

There  are,  beside  these,  a  number  of  attachments  which  are 
bolted  to  the  face  of  the  column  over  the  end  of  the  main  spindle 
and  connected  to  the  spindle  for  changing  the  direction  of  motion 
of  the  spindle  or  for  otherwise  modifying  this  motion  to  do  many 
kinds  of  work.  Milling-machine  attachments  include  those  for 
drilling,  slotting,  beveled  cutting,  vertical  milling  and  other 
purposes. 

345.  The  Boring  Machine. — There  are  two  general  types  of  this 
machine,  both  of  which  were  designed  primarily  for  boring  hollow 
cylinders  too  large  for  boring  on  the  lathe.  The  two  types  of  the 
boring  machine,  each  of  which  has  several  varieties,  are  (1)  the 
horizontal  boring  and  drilling  machine,  and  (2)  the  vertical  boring 
and  turning  mill.  These  machines  have  been  developed,  as  their 
names  indicate,  to  do  other  work  besides  boring. 


314  MECHANICAL  PROCESSES 

The  boring  of  large  gun  tubes,  small  gun  barrels,  and  long 
shafts,  which  may  be  forged  either  hollow  or  solid,  is  done  on  a 
special  type  of  lathe,  and  cannot  be  done  on  the  boring  machines 
here  mentioned. 

346.  The  Horizontal  Boring  and  Drilling  Machine. — Fig.  200 
shows  a  representative  type  of  this  machine.  A  cylinder  to  be 
bored  is  so  clamped  on  the  upper  cross-table  T,  and  the  table  is  so 
adjusted,  that  the  cylinder  axis  and  that  of  the  spindle  88  are 
coincident.  This  adjustment  is  made  by  raising  or  lowering  the 
main  table  MM  by  means  of  the  lever  B  which  works  the  large 


FIG.  200. — Horizontal  Boring  and  Drilling  Machine. 

screws  (7(7,  and  by  sliding  the  table  T  across  the  main  table.  The 
handle  D  moves  the  table  T  along  the  main  table.  The  faces  of  the 
tables  T  and  M  always  remain  horizontal,  and  the  tables  are  not 
moved  while  the  boring  is  in  progress.  The  main  table  is  sup- 
ported at  the  left  by  the  large  yoke  F. 

After  the  cylinder  is  adjusted,  a  boring  bar  with  suitable 
cutters  is  passed  through  the  cylinder  for  boring.  One  end  of 
the  bar  fits  into  the  end  of  the  main  spindle  8,  and  the  other  end  is 
supported  in  a  bushing  in  the  hole  G.  The  bar  with  its  cut- 
ters is  made  to  revolve  by  means  of  the  wheel  H,  which  is  driven  by 
the  belt  cones  and  back  gear  as  on  the  lathe.  The  bar  and  spindle  are 


THE  MACHINE  SHOP  315 

advanced  slowly,  while  they  revolve.,  by  the  feeding  mechanism  seen 
at  the  right  of  the  machine.  This  mechanism  is  fitted  to  give  the 
cutter  different  speeds  of  advancement  in  either  direction  of  the 
spindle's  length,  and  the  hand  wheels  are  fitted  to  change  the  posi- 
tion of  the  spindle  quickly  when  the  machine  is  not  in  operation. 

This  machine  has  the  advantage  of  being  able  to  bore  several 
parallel  holes  in  a  casting  without  having  to  re-adjust  the  casting 
on  the  table,  as  the  tables  themselves  provide  for  moving  the  sev- 
eral holes  into  position  for  the  cutters. 

Some  machines  have  an  upper  table  which  revolves  around  a 
vertical  axis  on  the  lower  table,  thus  fitting  them  for  boring  a 
series  of  holes  with  horizontal  axes  at  given  angles  one  to  another. 

The  ends  of  a  cylinder  may  be  faced  off  by  means  of  a  tool 
secured  to  the  attachment  Z.  This  attachment  is  bolted  to  the 
face-plate  P  and  the  tool  is  fed  to  cut  at  a  gradually  increasing 
distance  from  the  spindle  axis. ' 

A  drill  may  be  held  in  the  end  of  the  main  spindle  for  drilling 
holes  as  on  the  drilling  machine. 

347.  The  Vertical  Boring  and  Turning  Mill. — This  machine, 
shown  in  Fig.  201,  is  used  for  boring  large  steam  cylinders,  gun- 
hoop  forgings,  locomotive  drive-wheel  tires,  fly  wheels,  and  similar 
large  work.  This  work  may  also  be  faced  or  turned  on  the  ends, 
just  as  can  be  done  on  the  face  plate  of  a  lathe. 

Work  to  be  turned  or  bored  is  clamped  on  the  heavy  revolving 
table  T ,  which  revolves  on  a  vertical  axis.  This  table  is  virtually 
a  face  plate,  as  on  the  lathe.  The  housings  HE  of  the  machine, 
and  all  the  fittings  they  carry,  are  for  holding  rigidly  and  gov- 
erning the  movements  of  the  cutting  tools.  A  tool  is  clamped  in 
each  of  the  holders  BB  on  the  tool  bars  CO,  and  both  tools  may 
be  fed  independently  in  a  vertical,  horizontal,  or  slightly  inclined 
direction  as  desired.  Either  tool  may  cut  inside,  outside  or  on 
the  upper  end  of  a  piece  of  work. 

The  tool  bars  may  be  inclined  about  30°  on  the  swivel  head  DD, 
and  these  heads  are  readily  adjusted  along  the  cross  rail  RE.  The 
cross  rail  is  readily  adjusted  vertically  along  the  faces  of  the  hous- 
ings. The  tool  bars  are  raised  or  lowered  by  the  hand  wheels  on 
the  swivel  heads  when  adjusting  them  for  cutting  operations. 


316 


MECHANICAL  PROCESSES 


They  are  made  very  heavy  for  rigidity  and  their  weight  is  counter- 
balanced by  a  heavy  weight  on  the  ends  of  the  chain  K. 

The  mechanism  on  top  of  the  machine  adjusts  the  various  parts 
preparatory  to  operating  the  machine,  and  the  feed  mechanism  at 


FIG.  201. — Vertical  Boring  and  Turning  Mill. 

the  right  controls  the  feeding  of  the  tools  while  they  are  cutting. 
The  machine  is  driven  by  a  motor, not  in  view. 

Some  designs  of  this  machine  are  fitted  with  equipment  and 
attachments.,  not  here  shown,  for  many  varieties  of  machining,  in- 
creasing its  usefulness  particularly  in  saving  time  required  to  shift 
a  heavy  cylinder  to  another  machine  and  adjust  it  thereon. 


THE  MACHINE  SHOP  31? 

348.  The  Slotting  Machine. — A  type  of  this  machine  is  shown 
in  Fig.  202.  This  is  known  as  the  crank-driven  type  to  dis- 
tinguish it  from  the  heavier  gear-driven  type. 

The  slotting-machine  movements  resemble  very  much  those  of 
the  shaper.  The  machine  is  employed  particularly  for  slotting 
key  ways  in  the  hubs  of  wheels,  and  is  found  useful  for  much 


IT? 

D 


FIG.  202. — Slotting  Machine. 

other  slotting  of  various  kinds.  Work  is  clamped  on  the  horizontal 
table  A  which  may  be  adjusted  by  giving  it  (1)  a  circular  motion ; 
(2)  by  moving  it  horizontally  along  the  slides  B,  or  (3)  by  mov- 
ing it  horizontally  along  the  saddle  C  at  right  angles  to  the  motion 
of  (2).  These  motions  may  be  imparted  to  the  table  slowly  by 
the  feed  mechanism  D,  which  changes  the  position  of  the  work 
gradually  during  the  course  of  the  operation  of  slotting. 
21 


318 


MECHANICAL  -PROCESSES 


The  cutting  tool  moves  up  and  down  in  a  fixed  vertical  line 
perpendicular  to  the  face  of  the  table.  It  is  clamped  firmly  in 
the  yokes  G  at  the  end  of  the  ram  PI  which  works  in  the  guides 
KK .  The  ram  is  operated  by  the  connecting  rod  L,  the  upper  end 
of  which  swings  on  the  bolt  I/",  and  the  lower  end  of  which  is  held 
on  a  crank  pin  which  may  be  readily  adjusted  along  the  dovetail 
slot  in  the  disc  N  to  give  the  tool  a  greater  or  less  length  of  move- 
ment. The  weight  of  the  ram  is  counterbalanced  by  the  weighted 
lever  P.  The  disc  A7  is  on  the  end  of  the  main  spindle  which  is 
driven  with  a  quick  return  motion  by  the  large  wheel  R  geared  to 
the  driving  cones  S. 


FIG.  203. — Tools  for  the  Slotting  Machine. 

The  path  along  which  the  point  of  the  tool  moves  may  be  raised  or 
lowered  by  raising  or  lowering  the  ram  in  reference  to  the  nut  at  M. 

349.  Tools  for  the  Slotting  Machine. — Fig.  203  shows  a  few 
slotting-machine  tools  for  general  use,  although  many  forms  may 
be  made  for  special  uses.  They  are  designated  as  follows : 

(1-2)   Houghing  tools. 

(3)  Finishing  and  filleting  tool. 

(4)  Key  way  and  cutting-off  tool. 

(5)  Holder  for  tool  points  of  high-speed  steel. 

These  tools  are  made  to  cut  as  they  move  downward  in  the 
direction  of  their  length.  Other  tools  may  be  shaped  to  be  clamped 
on  the  ram  so  that  they  cut  in  a  direction  perpendicular  to  their 
length. 


THE  MACHINE  SHOP  319 

350.  Pipe  Cutting  and  Threading  Machines, — The  cutting  and 
threading  of  steam  and  gas  pipes  is  done  to  a  considerable  extent 
by  hand  appliances,,  but  the  best  results  are  obtained  by  a  machine 
which  cuts  and  threads  a  pipe  while  holding  it  rigidly  in  exact 
position.  These  machines  are  hand  or  power  driven,  or  may  be 
driven  by  hand  and  power. 

Pipe  cutting  and  threading  may  be  done  accurately  in  a  lathe, 
provided  the  pipe  is  not  too  long  for  the  lathe.  Pipe  threading  by 


FIG.  204. — Pipe-Cutting  and  Threading  Machine. 

means  of  hand  appliances  does  not  give  satisfactory  results  when 
many  short  lengths  of  pipe  are  to  be  joined  in  a  more  or  less 
intricate  system,  because  hand  appliances  cannot  usually  cut  a 
thread  so  that  a  pipe  will  turn  on  its  axis  while  screwing  it  into 
place. 

Fig.  204  shows  a  small  machine  which  grips  a  piece  of  pipe  in  a 
chuck  C  and  revolves  it  in  contact  with  a  cutting  tool  at  the  right 
of  the  machine.  The  die  head  D  also  carries  the  adjustable  thread 
chasers  which  thread  the  end  of  the  pipe. 


320  MECHANICAL  PROCESSES 

351.  Tool-Sharpening  Machines. — The  grindstone  is  still  em- 
ployed for  sharpening  metal-cutting  tools,  but  it  has  been  in  a 
great  measure  displaced  by  emery  or  carborundum  grinding  wheels. 

Many  types  of  tool-grinding  machines  are  now  common  among 
machine-shop  equipment.  One  of  the  smallest  consists  of  an  en- 
cased electric  motor  whose  shaft  carries  a  small  grinding  wheel 
on  each  end,  with  adjustable  rests  at  the  side  and  edge  of  each 
wheel  for  steadying  work  held  in  the  hand.  This  small  machine 
is  usually  mounted  on  a  bench. 

Another  type  much  used  is  the  heavy  wheel,  motor  driven, 
mounted  on  a  closed  base  and  partly  covered  by  a  hood. 

A  machine  shop  sometimes  has  machines  other  than  tool-grind- 
ing machines  especially  designed  and  built  for  very  accurate  circu- 
lar or  flat  grinding,  but  this  degree  of  accuracy  is  not  required  in 
the  usual  run  of  machine-shop  work. 

352.  Metal-Cutting   Saws. — It   is   frequently   necessary   to   cut 
bars,  rods,  standard  rolled  shapes,  etc.,  into  definite  lengths  for 
various  needs.     This  may  be  done  by  shearing  or  by  sawing,  and 
the  ox}f-acetylene  flame  is  now  used  for  metal  cutting  with  re- 
markable practical  success. 

The  sawing  machines  gives  smooth  ends  at  any  desired  angle  to 
the  axis  of  the  bar  sawed  without  wasting  much  metal. 

The  smaller  metal-sawing  machines  consist  essentially  of  a 
small,  straight  saw  blade  held  in  a  tightening  frame  and  dragged 
back  and  forth  across  the  work  to  be  sawed.  Machines  of  larger 
size  are  equipped  with  a  heavy  circular  saw  between  %  and  14  inch 
thick  and  between  12  and  30  inches  in  diameter.  The  saw  revolves 
slowly  and  is  fed  gradually  into  the  work  which  is  clamped  firmly 
on  the  table  of  the  machine. 

353.  Forcing  Presses. — These  are  used  for  forcing  wheels  on 
spindles  or  shafts.     They  vary  in  size  from  those  requiring  hand 
power  applied  through  screw  rods,  to  those  requiring  the  pressure 
of  a  heavy  hydraulic  cylinder.     A  heavy  hydraulic  forcing  press 
is  used  to  force  locomotive  drive  wheels  and  car  wheels  on  or  off 
their  axles,  to  force  electric  armatures  on  the  shafts  which  carry 
them,  and  to  force  wheels  and  crank  discs  on  engine  shafts. 


THE  MACHINE  SHOP  321 

354.  Machine-Shop  Notes. — Under  this  paragraph  will  be  given 
a  few  notes  applying  to  machine-shop  practice  in  general. 

(1)  The  cutting  speed  of  tools  is  determined  by  the  heat  gen- 
erated in  cutting.     When  the  tool  and  the  work  cannot  conduct 
this  heat  away  fast  enough  to  prevent,  the   tool   point   becomes 
heated  and  is  itself  ground  away.     This  condition  of  heating  is 
avoided   in   many   tools   like  milling  cutters.,  metal   saws,   rotary 
planer  cutters,  etc.,  where  each  tooth  does  not  cut  continuously. 
For  continuous  cutting  by  one  tool  point  as  in  the  lathe,  the  high- 
speed steels  are  much  superior  to  carbon  steel  for  removing  a  large 
quantity  of  metal,  but  carbon-steel  tools  are  better  for  the  lighter 
finishing  cuts.     Some  high-speed  steels  will  cut  satisfactorily  with 
the  tool  point  at  a  red  heat. 

(2)  Oil  or  soapy  water  applied  to  a  cutting  tool  assist  in  keep- 
ing down  the  temperature,  and  soapy  water  gives  a  smooth  bright 
surface  in  the  finishing  cut  of  iron  and  steel. 

Brass  is  cut  at  a  rapid  speed  and  is  just  brittle  enough  to  be 
given  a  smooth  surface  by  the  cutting  tool,  while  copper  is  difficult 
to  cut  by  machining  because  it  is  so  ductile  that  chips  do  not 
tear  away  readily. 

(3)  Work  is  secured  to  face  plates,  chucks,  planer  and  other 
machine  tables  by  bolts  or  clamps.     Care  must  be  taken  that  these 
fastenings  do  not  spring  the  work  so  that  the  machined  surfaces 
will  be  distorted  when  the  fastenings  are  removed.     It  is  well  to 
ease  up  the  fastenings  of  a  piece  of  work  just  before  taking  the 
finishing  cut,  leaving  enough  holding  pressure  to  keep  the  work 
from  slipping. 

(4)  Large  castings  which  are  to  be  machined  to  accurate  form 
and  dimensions  should  be  allowed  to  "  season "  for  a  few  weeks 
before  machining  is  done,  especially  if  these  castings  are  to  con- 
tain steam.     It  has  been  found  that  castings  undergo  a  gradual 
change  of  shape,  detected  only  by  careful  measurement,  soon  after 
having  been  cast.     This  is  of  particular  importance  with  castings 
for  steam  turbines  and  with  steam  cylinders.     In  case  a  casting  is 
hurriedly   needed,    as    in    emergency    repairs,    it   may   be    rough 
machined  after  casting  and  then  heated  slowly  and  evenly,  and 
allowed  to  cool  slowly. 


322 


MECHANICAL  PROCESSES 


(5)  To  safeguard  the  strength  of  metal,  a  fillet  should  always 
be  left  at  the  enclosed  angle  formed  by  the  junction  of  two  surfaces 
in  different  planes,  as  was  mentioned  in  the  chapter  on  pattern 
making. 

It  is  frequently  necessary  to  turn  a  shaft  to  two  diameters  as 
shown  in  Fig.  205.  A  straight  fillet  as  at  d,  or  better  a  rounded 
fillet  as  at  1),  should  always  be  left  at  the  junction  of  the  larger 
and  the  smaller  parts  of  the  shaft.  Another  style  of  fillet,  known 
as  a  liidden  or  Hind  fillet  may  be  used  where  those  like  ~b  or  d 
vrould  be  in  the  way,  as,  for  example  under  a  bolt  head,  as  at  k. 
Blind  fillets  are  advantageous  where  the  pins  and  journals  of  a 
crank  shaft  join  the  webs. 


FIG.  205. — Examples  of  Fillets. 

((>)  The  drilling  of  holes  with  large  twist  drills  is  increased  in 
speed  and  accuracy  by  first  drilling  a  small  hole,  say  %  of  an  inch, 
to  act  as  a  pilot  or  guide  hole.  . 

To  cut  a  hole  accurately  round  and  with  the  axis  in  a  given 
direction  is  not  a  simple  operation,  though  ordinary  bolt  or  rivet 
holes  do  not  require  any  such  degree  of  accuracy.  Hole-grinding 
is  accomplished  by  use  of  a  small,  rapidly  revolving  grinding  wheel 
of  less  diameter  than  the  hole  to  be  ground. 

A  round  hole  may  be  made  square  or  polygonal  by  broaching  out. 
This  consists  of  drawing  or  pushing  through  the  hole,  steel  pins 
of  such  cross  sections  as  will  cut  out  the  hole  to  the  shape  desired. 

(7)  Deep-hole  boring,  as  in  boring  gun  tubes,  gun  barrels  and 
propeller  shafts,  is  done  by  a  long  bar  which  carries  a  cutter  on 
one  end.  Either  the  work  or  the  cutter  bar  revolves  on  its  axis, 
and  the  bar  is  pressed  with  sufficient  firmness  against  the  work 
to  make  the  cutter  "  bite  "  so  long  as  the  rotary  movement  con- 
tinues. The  cutter  bar  and  cutter  must  be  hollow  to  keep  the 
work  cooled  by  a  circulation  of  water  through  this  hole.  This  also 


THE  MACHINE  SHOP  323 

flushes  away  the  chips  of  metal.  The  bar  is  not  as  large  in  diam- 
eter as  the  hole  bored  so  that  the  chips  can  be  washed  out.  Finish- 
ing to  the  required  outside  diameter  is  done  after  boring.  Small 
gun  barrels  are  held  vertically  to  be  bored,  to  keep  the  cutter  from 
being  drawn  to  one  side  of  the  barrel  by  gravity. 

(8)  In  machining  large  shafts  or  gun  tubes  made  from  forged 
steel  ingots,  the  cutting  away  of  the  superfluous  metal  in  the  lathe 
frequently  reveals   small   cracks  below   the   rough   surface   of   the 
forging.    These  cracks  are  caused  by  unequal  cooling  of  the  ingot, 
and  may  not  be  numerous  nor  large  enough  to  impair  seriously 
the  strength  of  the  forging,  but  each  crack  revealed  must  be  care- 
fully investigated  to  'determine  its  extent.     It  is  the  practice  to 
stop  the  lathe  when  one  of  these  cracks  is  revealed,  and  to  cut  out 
the  crack  with  a  cold  chisel.     If  its  depth  does  not  extend  below 
the  metal  to  be  machined  off  the  forging,  the  machining  is  again 
resumed. 

(9)  In  machinery  designations  the  terms  bearing  and  journal 
are  often  confused.    A  bearing  is  the  support  in  which  a  shaft  or 
axle  revolves,  and  a  journal  is  that  part  of  the  shaft  or  axle  which 
is  in  contact  with  the  bearing. 

355.  Bench  Work  in  the  Machine  Shop. — Some  work  in  the 
machine  shop,  as  chipping,  filing,  scraping  and  reaming,  is  done 
by  hand.  Cutting  threads  on  small  bolts  and  pipes  is  frequently 
done  at  the  bench,  although  such  work  is  not  economical. 

The  important  tools  and  equipment  much  used  in  bench  work 
are  as  follows,  many  of  which  are  well  known : 


(1)   Bench  vise. 

(9)   Scrapers. 

(2)   Hammers. 

(10)   Surface  plates. 

(3)   Cold  chisels. 

(11)   Hack  saw. 

(4)   Files. 

(12)    Copper  maul. 

(5)   Reamers. 

(13)   Abrasive  materials. 

(6)   Taps. 

(14)   Scriber. 

(7)   Dies. 

(15)    Center  punch. 

(8)   Wrenches. 

(a)   The  vise  has  jaws  hard   enough   to   resist  wear,  but   not 
brittle  enough  to  chip  off  when  struck  with  a  hammer. 


324  MECHANICAL  PROCESSES 

(b)  A  reamer  is  used  to  cut  a  drilled  hole  to  larger  diameter. 
Reamers  are  either  (1)  cylindrical  (called  straight  reamers)  for 
enlarging  holes  very  slightly  to  exact  cylindrical  form  and  given 
diameter.,  or  (2)  tapered  for  enlarging  holes  to  a  considerable  de- 
gree. The  end  of  a  straight  reamer  must  be  slightly  tapered  to 
allow  it  to  enter  the  hole  to  be  reamed  out.  The  straight  reamer 
soon  wears  enough  to  reduce  its  diameter  and  lose  its  accuracy  if 
used  for  any  except  light  cutting.  Expansion  reamers  have  been 
devised  to  be  sprung  out  as  they  wear. 

Rose  and  shell  reamers  are  made  for  use  on  lathes,  drills  and 
milling  machines.  A  rose  reamer  has  teeth  on  the  end  for  boring 
out  a  hole,  as  well  as  teeth  along  the  body  for  finishing  to  an  exact 
diameter. 


FIG.  206. — Cold  Chisels. 

(c)  The  hack  saw  is  very  handy  for  sawing  metal  bars  and  rods. 
It  consists  of  a  thin,  narrow  steel  saw-blade,  very  hard,  held  in  a 
bow  frame  of  steel  by  which  it  is  kept  stretched  taut. 

(d)  The  copper  maul  is  used  for  such  work  as  driving  a  finished 
shaft  into  the  hub  of  a  metal  wheel.    The  soft  copper  saves  marring 
the  finished  metal  surfaces. 

356.  Cold   Chisels. — These  are  usually  made  from  octagon-bar 
steel,  hardened  at  the  cutting  ends.     The  two  forms  most  used  are 
the  flat  chisel  A,  and  the  cape  chisel  B,  shown  in  Fig.  206.      The 
blade  of  B  is  much  narrower  than  that  of  A.     Other  forms,  as  the 
half-round  and  V-cornered,  are  very  useful. 

357.  Files. — The  many  kinds  of  files  are  classed  according  to 
(1)  length;  (2)  form  of  teeth,  and  (3)  shape  of  cross  section  of 
the  body  of  the  file. 

The  usual  forms  of  teeth  are  classified  as  shown  in  Fig.  207. 
There  are  finer-toothed  files  than  the  "  smooth,"  the  most  used  of 
which  is  the  "dead  smooth." 


THE  MACHINE  SHOP 


325 


In  cross-section,  the  usual  shapes  are  (a)  rectangular,  including 
mill,  flat,  pillar,  square  and  warding ;  (b)  round  or  partly  round, 


RASP. 


Coarse. 


DOUBLE  CUT. 


Coarse. 


SINGLE  CUT. 


Coarse. 


Bastard. 


Bastard. 


Bastard. 


»%M€&$ 


Second  Cut. 


Second  Cut. 


Second  Cut. 


Smooth.  Smooth.  Smooth. 

FIG.  207.— Styles  of  File  Teeth. 

inc-uding  half-round,  crossing,  tumbler,  pit-saw,  cabinet  cross-cut 
and  round;  and  (c)  triangular,  including  three-square,  and  knife- 
edge.  Some  rectangular  files  are  smooth  on  one  or  both  edges,  and 


326 


MECHANICAL  PROCESSES 


mill  or  flat  files  may  have  slightly  rounded  edges.    Fig.  208  shows 
the  cross-section  shape  of  files  most  used.    These  are : 


(1) 


(6) 


(3) 


Bound. 

(7)  Half-round. 

(8)  Three-square. 
Knife-edge. 
Cabinet. 


Flat. 
Mill. 
Pillar. 

(4)  Warding.  (9) 

(5)  Square.  (10) 

In  length  (measured  from  the  heel,  or  where  the  tang  begins) 
files  may  be  blunt  or  tapered,  and  the  usual  lengths  of  machine-shop 
files  vary  from  3  to  20  inches.  Smaller  sizes  of  files  for  special  uses 
are  known  as  needle  files. 

Another  type  of  file  has  recently  come  to  the  notice  of  machin- 
ists. This  is  a  single-cut  file  with  the  cuts  arranged  in  arcs  across 
the  length  of  the  file. 


m 


m 


3         4          5  6          7  Q 

FIG.  208. — Cross  Sections  of  Files. 


358.  Taps  and  Dies. — Thread  cutting  is  more  accurately  and 
economically  done  by  machine,  but  necessity  frequently  arises  for 
cutting  threads  by  hand.  Taps  and  dies  for  hand  work  are  made 
in  many  forms  and  sizes,  of  various  standards  of  threads.  They 
are  usually  made  for  cutting  right-handed  threads,  as  left-handed 
threads  are  used  only  for  some  particular  requirement. 

Fig.  209  shows  a  common  type  of  machinists'  hand  taps  for 
threading  nuts.  No.  1  is  a  taper  tap,  which  may  be  used  to  ream 
out  a  hole  and  start  the  cutting  of  threads  gradually,  distributing 
the  wear  along  the  tap.  No.  2  is  a  plug  tap  used  for  quicker  cutting 
than  No.  1.  No.  3  is  a  bottoming  tap  used  after  No.  2  for  cutting 
threads  to  the  bottom  of  a  hole. 

A  convenient  form  of  die  for  bolt  threading  by  hand  is  that 
shown  in  Fig.  210.  This  consists  of  a  holder,  made  up  of  several 
parts,  and  four  cutters.  An  extra  set  of  cutters,  or  "  chasers/7  is 
shown  beside  the  die.  These  cutters  may  be  adjusted  to  suit  ,rods 


THE  MACHINE  SHOP 


327 


FIG.  209. — Taps. 


FIG.  210.— Threading  Dies. 


328 


MECHANICAL  PROCESSES 


varying  about  1/32-inch  in  diameter  and  may  be  readily  removed 
for  renewing.  Fig.  211  shows  a  die-stock  A  used  for  holding  and 
turning  the  die,  and  an  adjustable  tap  wrench  B  for  turning  the 
taps  of  Figs,  209. 


FIG.  211. — Die  Stock  and  Tap  Wrench. 

All  taps  and  dies  are  marked  with  the  diameter  of  bolt  and  nut 
the}7  will  cut,  the  number  of  threads  per  inch,  and  the  class  or 
standard  to  which  the  thread  belongs. 


FIG.  212. — Forms  of  Wrenches. 

359.  Wrenches.' — Hand  wrenches  for  tightening  or  loosening 
nuts  are  of  several  forms,  some  of  which  are  shown  in  Fig.  212. 
The  wrenches  shown  are  designated  as  follows : 

(1)  Monkey  wrench  (adjustable). 

(2)  Pocket  wrench  (adjustable). 

(3)  Spanner  wrench. 


THE  MACHINE  SHOP  329 

(4)  Socket  wrench. 

(5)  Double-end,,  straight,  open,  hexagon  wrench. 

(6)  Double-end,  "  S,"  open,  square  wrench. 

(7)  Double-end,  angle,  open,  hexagon  wrench. 

(8)  Single-end,  closed  wrench. 

360.  Scrapers. — To  bring  perfect  contact  between  two  metal 
surfaces,  each  is  coated  with  a  fine  film  of  red  lead  and  oil,  and  the 
surfaces  are  then  rubbed  together.  Upon  separating  them,  the 
high  spots  may  be  plainly  seen,  and  are  removed  by  hand  scraping. 
The  scrapers  used  are  very  hard  pieces  of  steel,  not  unlike  files 
without  teeth,  as  shown  in  Fig.  213.  The  faces  are  ground  true 
to  form,  either  flat  or  curved,  and  the  ends  are  ground  blunt, 


FIG.  213.— Scrapers. 

except  that  the  end  of  D  is  at  more  or  less  an  acute  angle  to  the 
surface.  This  grinding  makes  sharp  edges  at  the  end  of  the 
scraper  and  the  scraping  is  done  with  these  edges. 

Bearings  are  scraped  to  fit  journals  by  this  method,  and  plane 
surfaces  which  move  upon  each  other  or  must  form  a  close  joint 
for  steam  or  other  pressure  connections,  are  brought  to  close  con- 
tact by  the  same  method.  Scraping  is  always  done  for  such  fitting 
after  the  parts  have  been  finished  as  accurately  as  can  be  done  by 
machining,  so  that  the  amount  of  scraping  needed  will  be  reduced 
to  a  minimum. 

Modern  machines  for  grinding  plane  and  curved  surfaces  are  so 
perfected  as  to  make  hand-scraping  unnecessary. 

361.  Surface  Plates. — For  testing  the  accuracy  of  a  surface 
which  must  be  exactly  plane,  one  of  the  surface  plates,  shown  in 


330  MECHANICAL  PROCESSES 

Fig.  214,  is  used.  These  plates  are  sold  in  pairs  so  that  one  may 
be  a  test  of  accuracy  of  the  other.  When  a  plane  surface  is  to  be 
tested,  one  of  the  plates  is  smeared  with  a  thin  coat  of  oil  colored 
slightly  with  red  lead.  This  coating  is  spread  evenly  by  rubbing 
both  plates  together  and  then  the  surface  to  be  tried  is  rubbed  over 
the  oiled  surface  of  one  of  the  plates.  High  spots  will  be  revealed 
by  the  oil  coating,  and  these  are  scraped  down. 

The  making  of  surface  plates  requires  that  each  of  three  plates 
shall  be  scraped  to  fit  the  other  two  to  insure  plane  surfaces. 

362.  Abrasive  Materials. — These  are  used  for  polishing  metal 
surfaces  by  grinding  away  the  marks  left  by  the  file  or  by  machine- 
cutting  tools.  They  are  frequently  seen  in  the  forms  known  as 
emery,  carborundum,  and  crocus  cloths.  These  are  made  up  of 
a  cloth  of  considerable  strength,  covered  on  one  side  with  fine 


FIG.  214. — Surface  Plates. 

particles  of  the  abrasive  material,  held  by  a  coating  of  glue.  These 
cloths  are  numbered  according  to  the  coarseness  of  the  grains  glued 
thereon.  Crocus  cloth  is  covered  with  red  oxide  of  iron,  and  is 
used  for  fine  polishing. 

Powdered  grinding  materials  are  also  frequently  used  mixed 
with  oil  for  grinding  between  two  metal  surfaces  in  contact. 

363.  Portable  Tools. — There  is  frequent  necessity  for  drilling 
and  other  cutting  on  work  which  cannot  be  moved  to  a  machine. 
There  have  been  devised  many  types  of  small  portable  machines, 
usually  designated  as  portable  tools,  which  can  be  readily  trans- 
ported to  large  work  for  effective  use  in  drilling,  chipping,  grind- 
ing away  rough  places,  and  cutting-off. 

For  machine-shop  use  the  list  of  portable  tools  generally  con- 
sists of  the  following  viz. : 

(1)  Various  types  of  portable  drills  driven  by  electric  or  pneu- 
matic power  or  by  hand.  The  ratchet  drill  for  hand  drilling  is 
the  simplest  and  lightest  of  these  types. 


THE  MACHINE  SHOP 


331 


(2)  Portable  boring  bar,   motor   driven,   for  boring  the  stern 
bearings  of  ships  before  launching. 

(3)  Valve  re-seating  machine,  hand  or  electrically  driven,  for 
truing  up  the  seats  of  valves  which  have  become  leaky  in  use. 
This  is  done  without  removing  the  valve  body  from  its  pipe  line. 

(4)  Pneumatic  hammers  for  driving  a  cold  chisel  for 
many  kinds  of  surface  or  edge  chipping  and  for  cutting 
a  narrow  path  across  a  piece  of  metal  in  cutting  it  off. 

(5)  Pneumatic  and  electric  grinders.     These  are  es- 
sentially small  grinding  wheels  mounted  on  a  suitable 
shaft  so  supported  that  the  machine  can  be  held  in  the 
hands  and  the  revolving  wheel  pressed  against  the  spot 
to  be  ground. 

(6)  The   oxy-acetylene   blowpipe.      This    is   used   to 
direct  its  flame  along  a  path  on  a  metal  plate,  burning 
its  way  through  the  plate.     It  is  used  for  many  cutting 
operations  in  bridge,  boiler,  ship  and  other  work,  and  is 
very  useful  as  a  portable  cutting  apparatus,  though  it  of 
course  leaves  rough  edges  at  the  sides  of  the  path  burned 
through  by  the  flame. 

(7)  Very  useful  also  in  various  shops  are  lifting  jacks 
and  the  differential  pulley. 

Jacks  are  made  for  lifting  either  by  screw  or  hydraulic 
power.  They  exert  great  force  and  can  be  operated 
usually  by  one  man.  A  hydraulic  jack  which  will  lift 
50  tons  a  distance  of  18  inches  weighs  about  325  pounds 
and  can  be  carried  by  two  men.  Dilute  alcohol  is  much 
used  in  the  hydraulic  jack  because  it  does  not  freeze,  but 
it  lacks  the  desired  quality  as  a  lubricant. 

The  differential  pulley,  shown  in  Fig.  215,  may  be 
operated  by  one  man  to  lift  weights  ranging  considerably 
beyond  a  ton,  according  to  its  capacity.  It  consists  of  a  double- 
sheaved  wheel,  or  block,  at  the  top  and  a  single-sheaved  wheel  below. 
An  endless  chain  is  rove  over  these  sheaves.  The  distance  between 
the  two  wheels  is  increased  or  decreased  by  pulling  one  side  or  the 
other  of  the  loose  part,  or  bight,  B  of  the  chain.  The  lifting  power 
is  due  to  the  fact  that  the  two  sheaves  of  the  upper  wheel  are  of 
slightly  different  diameters. 


PIG.  215. 

Differential 

Pulley. 


332 


MECHANICAL  PROCESSES 


364.  Pipe  Fitting. — This  is  the  term  used  to  designate  tho  work 
of  putting  together  various  lengths  of  piping  and  their  connecting 
parts.  This  work  is  associated  with  the  machine  shop,  where  the 
required  lengths  of  piping  are  usually  cut  and  threaded.  The  con- 
necting parts  are  known  as  fittings.  They  are  made  in  certain 
standard  forms  as  a  branch  of  re-manufacturing,  and  are  kept  in 
quantities  among  the  supplies  of  the  machine-shop  store-room. 


FIG.  216.— Example  of  Pipe  Fitting. 

The  piping,  used  so  extensively  for  conveying  steam,  water  and  gas, 
in  many  requirements  other  than  those  of  engineering,  is  described 
in  the  chapter  on  the  re-manufacture  of  metals.  The  standardiza- 
tion of  the  sizes  and  threads  of  fittings  to  agree  with  standard  sizes 
and  threads  of  piping  makes  it  possible  to  use  together  the  fittings 
and  piping  of  all  manufacturers.  However,  difficulty  is  occa- 
sionally found  in  pipe-fitting  work  due  to  the  fact  that  the  slightly 
tapered  threads  on  both  pipe  and  fittings  are  cut  too  deep  or  too 
shallow. 


THE  MACHINE  SHOP 


333 


Refer- 
ence 
No. 

Fitting. 

Size. 

Style. 

j 

Globe  valve                                  

V 

9 

si.tr 

y 

w 

4 

34" 

5 

a/,  n 

g 

s/.rr 

ij> 

1" 

3 

34" 

9 

1" 

10 

V 

11 

do  

3/k" 

12 

Toe 

8/i" 

Malleable  beaded 

13 

do                         

Sj.fr 

Malleable  plain 

14 

do                                  ...           

•Lf.ll 

Malleable  beaded 

15 

Bii""Vl" 

Do 

if? 

3  .^vVvl'' 

Do 

%rr 

18 

Cross    

3a" 

Malleable  beaded 

19 

3,,'r 

°0 

Elbow  

i" 

Malleable  plain 

91 

do 

%^/ 

Do 

99 

Reducinir  elbow  

3/j/'\i" 

Cast  iron 

93 

Side-outlet  elbow  

i" 

Malleable  plain 

91 

Street  elbow  . 

3/i" 

95 

45°  elbow  

a,// 

Do 

9fl 

1" 

Cast  iron 

97 

Sleeve  couplin°r  

\H 

28 

W\\" 

Malleable,  plain. 

99 

do      

3/l"\l" 

Do. 

30 

I.// 

Do. 

QI 

^>"X3/i" 

3° 

(JO                                  

3/t"xl" 

33 

^o" 

34 

3/l" 

Malleable,  beaded 

35 

1" 

36 

1" 

37 

Cap      ..        

W 

38 

do  

34" 

39 

do 

i0^ 

40 

Plug          

3/t" 

41 

do 

%^/ 

4° 

.do  

3Zi" 

22 


334  MECHANICAL  PROCESSES 

Pipe  threads  are  usually  right  handed,  though  left-hand  threads 
are  used  for  special  purposes.  The  pipe  ends  are  always  threaded 
on  the  outside  and  most  of  the  fittings  are  threaded  to  screw  on  the 
pipe  end,  although  some  fittings  are  made  with  outside  threads  to 
be  screwed  into  other  fittings.  In  connecting  pipe  and  fittings,  the 
threads  are  swabbed  with  a  mixture  of  oil  and  graphite  to  make  a 
tight  joint  which  may  be  taken  apart  any  time  afterward. 

365.  Fittings. — Fig.    216    is  a    specimen    of    pipe-fitting    work 
made  up  to  show  the  use  of  various  types  of  fittings.     The  kind, 
size,  and  style  of  each  fitting  is  given  in  the  preceding  list. 

Fittings  are  usually  made  of  brass,  cast  iron,  or  malleableized 
cast  iron.  The  malleableized  cast-iron  fittings  are  known  as 
malleable  fittings  and  are  adapted  to  high  pressures.  They  are 
made  in  two  styles  known  as  beaded,  with  a  rolled  rim  at  the  open- 
ing of  the  fitting;  and  plain,  without  this  rim. 

Cast-iron  fittings  are  much  more  bulky  than  the  malleable  fit- 
tings and  are  used  for  pressures  not  over  about  150  pounds  as  they 
are  not  elastic,  although  they  may  not  burst  under  many  times 
that  pressure.  Brass  fittings  (known  as  composition  fittings)  are 
used  for  their  ornamental  appearance. 

Iron  fittings  are  either  Hack  or  galvanized. 

Pipe  fittings  of  large  size  or  for  use  under  high  pressures  are 
made  with  flanged  instead  of  screwed  ends.  Special  fittings  are 
made  for  hydraulic  pipe  connections. 

366.  Tools  Used   in   Pipe  Fitting. — The  hand  tools   ordinarily 
used  in  pipe  work  are  shown  in  Fig.  217.    The  pipe  vise  holds  pipe 
for  cutting,  threading  and  fitting  parts  together.     The  tongs  and 
wrenches  grip  the  pipe  for  holding  or  turning.     Dies,  made  with 
standard  threads,  are  held  in  the  die  stock  when  in  use.    Each  size 
of  pipe  die  has  a  bushing  which  fits  in  the  stock  behind  the  die  to 
steady  the  stock  on  the  pipe  end. 

367.  Bolts,  Nuts  and  Machine  Screws. — These  articles  are  prod- 
ucts of  the  re-manufacture  of  metals.     Those  for  general  use  are 
made  according  to  adopted  standards  of  shape  and  size. 

A  machine  screw  is  a  small  bolt  with  a  slot  in  the  head  to  be 
turned  by  a  screw  driver.  Machine  screws  are  made  in  diameters 


THE  MACHINE  SHOP 


335 


designated  by  gage  numbers,  and  varying  over  a  range  from  about 
1/16  to  1/2  inches  in  diameter.  Machine  screws  with  nuts  are 
called  stove  bolts. 


FIG.  217.— Pipe-Fitting  Tools. 

Bolts  are  standardized  in  the  following  items,  viz. 

(1)  Length. 

(2)  Diameter. 

(3)  Threads  per  inch  for  a  given  diameter. 

(4)  Shape  and  dimensions  of  head. 


336 


MECHANICAL  PROCESSES 


Nuts  are  standardized  in  shape  and  dimensions.  A  nut  is 
usually  larger  than  the  head  of  its  bolts  as  it  is  essential  that  the 
side  of  the  nut  through  its  smallest  part  should  be  large  enough  to 
give  it  the  strength  needed. 


A  CD 

FIG.  218.  —  Standard  Bolts. 

Fig.  218  shows  the  usual  types  of  standard  machine  bolts. 
These  are  designated  as  follows,  viz.  : 

A.  Machine  bolt,,  square  head  and  nut. 

B.  Machine  bolt.,  hexagon  head  and  nut. 

C.  Machine  bolt,  round  or  fillister  head. 

D.  Carriage  bolt. 

E.  Stud  bolt. 

F.  Stud  bolt  with  collar. 

G.  Tap  bolt  or  cap  screw  (the  same  as  A,  B,  or  (7),  without  nut 
and  with  longer  thread. 


O          CD 


/  2  3  * 

FIG.  219. — Forms  of  Machine-Screw  Heads. 

Fig.  219  shows  the  usual  forms  of  machine-screw  heads. 
They  are  designated  as  follows: 

1.  Flat  or  countersunk.  3.  Oval  countersunk. 

2.  Eound  or  button.  4.  Fillister. 


THE  MACHINE  SHOP  337 

Among  the  special  forms  of  bolts  may  be  mentioned  the  fol- 
lowing, viz. : 

(1)  The  body-bound  bolt,  also  called  the  tight-fitting  bolt,  is 
one  which  is  turned  in  a  lathe  to  fit  closely  a  bored  hole.     Bolts 
of  this  kind  are  much  used  in  holding  together  parts  of  machinery 
to  prevent  the  slightest  change  of  position  of  one  part  on  another. 

(2)  The  set  screw  is  used  to  screw  through  the  hub  of  a  wheel 
and  press  against  the  shaft  to  hold  the  wheel  in  place.     It  has 
many  other  similar  uses.     It  resembles  a  tap  bolt,  and  is  either 
pointed  or  cupped  at  the  end  to  take  good  hold  against  the  shaft. 

(3)  The  expansion  bolt  is  used  for  bolting  brackets  and  fixtures 
to  a  stone,  brick  or  cement  wall.     The  bolt  has  an  expanding  nut 
which  is  placed  in  a  hole  dug  in  the  wall.     When  the  bolt  is 
screwed  in  tightly,  it  expands  the  nut  and  makes  it  press  tightly 
in  the  hole. 

The  length  of  a  bolt  does  not  include  the  head,  except  in  the 
case  of  bolts  with  countersunk  heads.  It  is  generally  understood 
that  bolts  have  standard  right-hand  threads,  and  if  bolts  with  left- 
hand,  double  or  other  than  standard  threads  are  desired  they  must 
be  specified. 

To  prevent  nuts  jarring  loose  and  unscrewing,  various  nut  lock- 
ing devices  are  used. 


CHAPTER  XII. 
THE  BOILEU  SHOP. 

368.  Work  of  the  Boiler  Shop. — The  work  of  building  a  boiler 
is   partly   that  of   shaping   flat   steel   plates   into   cylindrical   and 
flanged  forms,  and  partly  that  of  assembling  with  these  forms  cer- 
tain products  of  other  shops,  as  tubes,  corrugated  furnaces,  stay 
bolts,  etc.     The  whole  assemblage  composing  the  boiler  proper  is 
fastened    together   by    rivets,    screwed    stays,    and    expanded    tube 
ends;  and  when  ready  for  use  the  boiler  is  supplied  with  such 
fixtures  as  the  uptake  and  the  smoke  pipe,  which  are  built  in  the 
boiler  shop,  and  with  such  fittings  as  steam  gage,  stop  valve,  safety 
valve,  etc.,  furnished  by  other  shops. 

369.  Types  of  Boilers.    Their  Manufacture. — The  many  types  of 
boilers  may  be  classed  under  two  general  divisions,  viz. : 

(1)  Shell  or  fire-tube  boilers. 

(2)  Pipe  or  water-tube  boilers. 

The  shell  boiler  is  made  in  several  forms,  of  which  the  loco- 
motive and  the  cylindrical  or  Scotch  marine  types  are  familiar 
examples.  In  general  design  the  shell  boiler  is  in  the  form  of  a 
cylindrical  shell  which  is  a  reservoir  for  the  water  and  steam.  At- 
tached to  the  shell,  and  more  or  less  surrounded  by  it  are  (1)  a 
fire  box,  or  one  or  more  cylindrical  steel  furnaces  and  their  com- 
bustion chambers,  and  (2)  a  nest  of  tubes  opening  from  the  fire 
box  or  combustion  chambers  into  the  smoke  pipe. 

The  water-tube  boiler  consists  of  an  assemblage  of  straight  or 
bent  tubes,  the  ends  of  which  open  into  water  and  steam  reservoirs 
usually  designated  respectively  as  headers  and  drums.  The  water 
and  steam  are  contained  in  these  tubes,  headers  and  drums,  and  the 
boiler  is  surrounded  by  a  sheet-steel  casing  which  confines  the  fire 
and  smoke  within  its  limits.  A  space  for  the  furnace  is  provided 
under  the  tubes  and  the  flame  and  hot  gases  pass  among  the  tubes 
to  reach  the  smoke  pipe. 

The  shell  boiler  held  supremacy  for  many  decades  as  a  steam 
generator  after  the  steam  engine  came  into  use,  but  demand  for 


THE  BOILER  SHOP 

the  economy  of  higher  steam  pressures  has  gradually  brought  into 
use  many  types  of  the  water-tube  boiler,  which  is  particularly 
adapted  to  standing  high  pressures.  This  change  has  taken  away 
much  work  from  the  shop  for  building  shell  boilers.  The  building 
of  water-tube  boilers  consists  in  a  great  measure  of  the  assembling 
of  the  products  of  other  shops  and  plants,  and  of  the  making 
of  certain  parts  by  the  cold  or  hot  pressing  of  mild  steel  plates  to 
special  forms,  leaving  very  little  work  to  be  done,  for  this  type  of 
boiler,  by  the  methods  and  machines  used  in  the  building  of  shell 
boilers. 

The  many  patented  types  of  water-tube  boilers  have  brought 
about  the  building  of  these  boilers  as  special  work,  and  many 
of  the  processes  of  forming  the  headers  and  other  parts  of  a 
particular  type  of  boiler  are  unique  and  ingenious  methods  of  hot 
and  cold  pressing  and  of  welding  by  aid  of  electric,  furnace,  and 
gas  blow-pipe  heat. 

In  some  patented  boilers  the  parts  are  made  up  more  or  less  of  cast 
steel,  or  even  of  cast  iron  for  pressures  not  over  about  100  pounds. 

Many  shell  boilers  for  high  and  low  pressures  are  still  built  for 
marine,  locomotive,  and  stationary  uses,  also  the  larger  drums  and 
some  other  parts  of  water-tube  boilers  are  built  in  the  shop 
equipped  for  shell-boiler  work,  hence  the  boiler  shop  and  its  equip- 
ment continue  to  be  an  essential  part  of  a  general  manufacturing 
plant. 

The  improvement  in  recent  years  of  boiler  steel  enables  shell 
boilers  to  be  built  for  higher  pressures  than  formerly. 

370.  Boiler  Material. — The  material  used  for  plates,  rivets, 
braces,  and  all  other  parts  on  which  the  structural  strength  of  a 
high-grade  boiler  depends  are  made  of  a  low-carbon  open-hearth 
steel  in  which  is  allowable  only  very  small  quantities  of  phosphorus 
and  sulphur.  Nickel  is  often  alloyed  with  this  steel  to  improve  its 
tensile  and  elastic  strength. 

The  elastic  strength,  rather  than  the  tensile  strength  of  the 
material,  is  of  first  importance,  as  the  permanent  safety  of  the 
boiler  depends  upon  all  stresses  remaining  within  the  elastic  limit. 
A  good  margin  between  the  elastic  and  the  final  strength  of  the 
material  provides  a  ductility  or  elongation  which  will  many  times 
save  actual  and  disastrous  disruption  under  pressure  by  allowing 


340 


MECHANICAL  PROCESSES 


the  material  to  bulge  out  or  otherwise  stretch  greatly  before  it 
breaks. 

Specifications  for  high-grade  boiler  plate  require  an  elastic 
strength  of  about  %  the  tensile  strength,  a  tensile  strength  of  about 
70,000  pounds,  and  an  elongation,  when  pulled  apart,  of  about 
25%  in  a  test  bar  8  inches  long.  Rivets,  bolts,  and  material  for 
boiler  braces  are  required  to  exceed  slightly  the  requirements  speci- 
fied for  plates.  Plates  which  are  to  be  flanged  for  parts  of  the 
boiler  structure  must  be  ductile  to  a  high  degree,  and  specifications 
usually  require  the  test  piece  to  show  a  slightly  greater  per  cent 
of  elongation  and  allow  slightly  less  tensile  and  elastic  strength 
than  for  other  plates. 


Top  Center 


FIG.  220. 

371.  Preliminary  Diagram  for  Laying  Out  Work. — The  dimen- 
sions and  all  details  of  a  boiler  to  be  built  must  be  shown  on  suit- 
able drawings  for  the  guidance  of  the  master  boilermaker  in  laying 
out  and  directing  the  work  of  building  the  boiler.  Supposing  a 
cylindrical  shell  boiler  is  to  be  built,  the  drawings  supplied  must 
give  at  least  a  longitudinal  and  a  transverse  cross  section  of  the 
boiler,  besides  views  of  the  side  and  one  or  both  end  elevations, 
and  sufficient  enlarged  views  of  single  or  combined  parts  to  show 
the  details  of  their  construction. 

From  the  drawings  he  proceeds  to  mark  out  to  full  or  half  size 
on  a  smooth  laying-out  board  provided  for  the  purpose,  the  front 
end  of  the  boiler.  The  beginning  of  this  work  is  shown  in  Fig. 


THE  BOILER  SHOP 


341 


220.  Through  the  center,  0,  of  the  boiler,  draw  the  horizontal  and 
vertical  lines  as  guides  for  laying  down  all  parts  of  the  boiler  head 
and  the  openings  therein.  This  board  serves,  also  to  show  on  a 
large  scale  the  relative  positions  of  interior  parts  of  the  boiler, 
particularly  the  positions  of  the  plates  composing  the  combustion 
chambers. 

The  shell  of  the  boiler  is  composed  of  two  or  more  rings  or 
courses  of  plates,  each  course  consisting  of  one  or  more  plates,  as 


FIG.  221. — Double-End  Cylindrical  Boiler. 

shown  in  Fig.  221.  The  plates  in  each  course  are  butted  end  to 
end,  and  are  fastened  together  by  butt  straps  on  both  sides  of  the 
plates.  An  outer  butt  strap  is  marked  in  the  figure.  Two  adjacent 
courses  are  joined  together  by  overlapping  the  ends  as  shown,  and 
the  ends  of  the  shell  overlap  the  heads. 

Eeferring  to  Fig.  220,  the  full-line  circles  represent  the  ends  of 
the  inner  and  outer  course  plates,  and  the  dotted  lines  represent 
the  neutral  circles  of  these  plates  by  which  their  curvatures  are 
figured  from  the  flat  plates  from  which  they  are  made.  The  lines 
through  the  center  0  divide  the  diagram  into  quadrants,  deter- 
mining four  points  of  reference  for  laying  out  the  shell. 


342  MECHANICAL  PROCESSES 

372.  Diagram  for  Laying  out  Shell  Plates.— The  shell  is  de- 
veloped on  a  flat  surface,  the  position  of  each  plate  joint  is  marked 
with  reference  to  the  top,  bottom,  and  side  center  lines,  which  are 
the  first  lines  placed  on  this  diagram,  and  the  amount  of  lap  for  the 
plates  of  each  adjacent  course  is  marked.     All  details  of  rivet  and 
other  holes   are   transferred   to  this   diagram,   which  is   used  for 
marking  each  shell  plate  and  their  butt  straps.    Each  end  of  each 
plate  is  numbered  when  it  is  measured  up,  to  insure  placing  it  in 
its  proper  location. 

The  developing  of  the  shell  is  virtually  cutting  it  along  one  of 
its  cylindrical  elements  and  unrolling  it  until  it  lies  flat.  This 
development  is  made  as  if  the  outer  courses  unrolled  without 
stretching  the  circumference  of  their  neutral  circle,  but  the  inner 
course  neutral  circle  is  supposed  to  be  stretched  until  it  equals  the 
length  of  the  outer  course  circle  in  the  flat  diagram. 

In  marking  off  rivet  holes  around  the  girth  of  the  shell,  care 
must  be  taken  to  space  them  so  that  they  will  be  at  equal  distances 
apart  around  the  circle. 

The  distance  between  centers  of  adjacent  rivet  holes  is  called  the 
pitch  of  the  rivets. 

373.  Preparation  of  Plates  for  Laying  Out. — Boiler  plates  are 
ordered  from  the  rolling  mill  as  flat  plates.    Their  dimensions  are 
determined  from  the  drawing  of  the  boiler,  and  the  plates  ordered 
should  be  near  their  finished  dimensions,  leaving  a  margin  of  about 
once  the  thickness  of  the.  plate  to  be  trimmed  off  around  the  edges. 
The  trimming  of  this  margin  by  chipping  or  planing  removes  the 
strained  metal  along  the  edges  caused  by  shearing  the  plate  at  the 
mill. 

A  few  days  before  a  plate  is  needed  for  laying  out,  it  is  selected 
from  stock  and  pickled  to  loosen  scale  and  to  expose  the  clean 
surface  of  the  steel.  Pickling  is  done  by  immersing  the  plate  on 
edge  for  about  24  hours  in  a  wooden  vat  containing  about  5%  of 
hydrochloric  acid  in  fresh  water.  When  lifted  out  the  plate  is 
scrubbed  and  rinsed  with  clean  water  made  slightly  alkaline  with 
lime  to  remove  all  acid. 

A  careful  record  of  each  plate,  giving  dimensions,  weight,  and 
data  of  its  manufacture  and  tests,  is  furnished  the  master  boiler- 


THE  BOILER  SHOP  343 

maker.  This  record  enables  the  selection  of  the  particular  plate 
intended  for  a  certain  place  in  the  boiler. 

Laying  out  consists  of  transferring  to  the  clean  surface  of  a 
plate  the  dimensions  and  lines  shown  by  the  laying-out  diagrams 
and  the  original  drawings.  The  location  of  lines  and  boundaries 
is  marked  on  a  plate  by  scribed  lines  and  by  center-punch  marks. 

374.  Operations  for  Shaping  Plates. — The  operations  for  shaping 
boiler  plates  are  as  follows : 

(1)  Planing  plate  edges. 

(2)  Rolling  plates  to  cylindrical  form. 

(3)  Flanging. 

(4)  Drilling  holes  for  rivets,  stay  bolts,  tubes,  etc. 

These  operations  prepare  the  plates  for  assembling,  although  a 
few  rivet  holes  are  drilled  immediately  after  the  plates  are  marked, 


FIG.  222. 

» 

for  the  purpose  of  handling  them.  These  holes  are  drilled  slightly 
smaller  than  the  finished  size  and  their  worn  edges  are  reamed  out 
when  ready  for  riveting. 

375.  Planing  Plate  Edges. — Edges  of  shell  plates  are  planed  to 
the  finished  dimensions  before  the  plates  are  rolled.  When  the 
boiler  head  is  made  up  of  more  than  one  plate,  the  straight  edges 
of  these  plates  are  planed,  but  the  edges  10  be  flanged  are  not 
planed.  Flanged  edges  are  chipped  smooth  by  pneumatic  chippers, 
or  a  circular-flanged  plate  forming  a  boiler  or  steam-drum  head 
may  have  its  flanged  edge  turned  smooth  in  a  large  lathe. 

Shell-plate  ends  which  butt  together  must  be  planed  at  the 
correct  angle  to  fit  at  both  outer  and  inner  edges  when  rolled  to 
shape,  as  shown  at  a,  Fig.  222.  All  free  edges,  as  those  marked  & 
on  the  butt  straps,  are  planed  or  chipped  to  a  bevel  for  caulking, 
the  usual  angle  of  which  is  shown  in  the  section  of  a  plate  edge  of 
thickness  t. 


344 


MECHANICAL  PROCESSES 


Fig.  223  shows  a  plate-edge  planer.  The  plate  rests  flat,  and 
the  edge  to  be  planed  is  clamped  by  the  screw  jacks  J  against  the 
bedplate  B  of  the  machine.  The  clamping  beam  C  is  held  rigidly 
by  the  housings  H.  Two  saddles,  8  and  T,  which  travel  along  the 


FIG.  223.— Plate-Edge  Planer, 

bedplate,  carry  the  cutting  tools.  The  saddle  8  carries  two  tools 
and  cuts  in  both  directions  of  its  travel.  The  saddle  T  carries  but 
one  tool  which  may  be  fed  vertically  during  its  horizontal  motion. 
The  saddles  are  used  separately.  The  bar  K  is  an  automatic  revers- 
ing bar  for  reversing  the  motion  of  the  two-way  cutting  saddle. 


FIG.  224.— Plate-Bending  Rolls. 

376.  Plate-Bending  Rolls. — This  name  is  given  to  the  machine 
shown  in  Fig.  224  to  distinguish  it  from  the  plate  straightening 
rolls.  The  machine  consists  of  three  solid-forged  rolls  supported 
parallel  in  heavy  bearings.  The  lower  rolls  are  driven  by  gearing 


THE  BOILER  SHOP  345 

and  the  upper  roll  revolves  from  contact  with  the  plate  rolled.  The 
upper  roll  may  be  raised  or  lowered  to  suit  the  thickness  of  the  plate 
and  the  curvature  to  which  it  is  rolled.  In  case  a  sheet  is  rolled 
into  a  complete  cylinder,  it  is  removed  by  lifting  one  end  of  the 
upper  roll  and  sliding  the  cylinder  out.  To  do  this,  the  yoke  K 
is  screwed  down  against  the  extension  bar  B  until  the  other  end  of 
the  roll  and  its  bearing  are  lifted  out  of  the  way. 

Plates  are  rolled  cold,  and  are  run  back  and  forth  until  the  cur- 
vature gradually  increases  to  that  of  a  template  made  as  a  guide. 

The  rolls  cannot  bend  a  plate  for  a  short  distance  from  each  end, 
as  shown  by  the  diagram  in  Fig.  225.  Suppose  the  plate  to  be 


FIG.  225. 

moving  in  the  direction  of  the  arrow  p.  That  part  of  the  plate 
between  its  contact  points  with  the  rolls  B  and  C  is  not  bent,  as 
bending  takes  place  only  after  the  plate  passes  the  first  contact 
point  K  with  the  roll  B.  When  the  plate  reaches  such  a  position 
that  the  end  J  has  passed  over  the  crest  of  the  roll  C  and  begins  to 
drop,  practically  no  further  bending  will  take  place  between  the  end 
and  the  point  K.  In  shop  practice,  this  difficulty  is  obviated  by  plac- 
ing a  bar  of  half-round  iron  at  M  and  rolling  it  against  the  plate. 

The  lower  rolls  have  one  or  more  longitudinal  notches,  as  at  GG,  to 
grip  the  edge  of  the  plate  when  started  in  the  rolls,  or  to  flange 
the  ends  of  narrow  strips  of  plating  when  needed. 

Plate-bending  rolls  are  also  made  to  operate  in  a  vertical  posi- 
tion, and  are  known  as  vertical-bending  rolls. 


346 


MECHANICAL  PROCESSES 


377.  Marking  a  Flange. — In  boiler  making  and  in  sheet-metal 
work  generally,  a  flange  is  a  margin  of  metal  along  the  edge  of  a 
plate  turned  at  a  greater  or  less  angle  out  of  the  plane  of  the  plate. 

Fig.  226  shows  a  cross  section  of  a  flanged  circular  plate  with 
the  dimensions  which  would  be  given  by  a  drawing.  The  lettering 
has  been  added  for  purposes  of  explanation.  AB  is  the  center  line 
of  the  drawing,  M  is  a  point  at  the  end  of  the  curve  of  the  flange, 
t  is  the  thickness  of  the  plate,  and  r  is  the  radius  of  the  inner 


FIG.  226. 

curvature  of  the  flange.  The  distance  r+t  is  called  the  "draw" 
of  the  flange. 

The  marking  of  the  flat  plate,  shown  in  Fig.  227,  consists  of 
locating  the  point  M  so  that  it  will  be  24  inches*  from  the  center 
line  AB  when  the  flange  is  turned.  From  C  as  a  center  describe 

on  the  plate  a  circle  with  a  radius  of  24+  — i—  inches.    This  circle 

is  marked  with  a  series  of  center-punch  marks,  as  at  M',  as  a  guide 
to  the  workman  in  turning  the  flange,  and  these  punch  marks  must 
be  turned  into  the  position  occupied  by  M  in  the  upper  figure.  The 


FIG.  227. — Marking  a  Plate  for  Flanging. 

plate  must  have  sufficient  diameter  to  allow  for  the  flange  width 
MN  of  3%  inches,  plus  a  small  amount  for  chipping  to  a  smooth- 
beveled  caulking-edge.  The  distance  -^i-  is  arbitrarily  added  in 

shop  practice  to  the  radius  prescribed  by  the  drawing  as  an  allow- 
ance for  the  change  of  position  of  the  punch  marks  when  the  flange 
is  turned. 

378.  Methods   of   Flanging. — Flanges   may   be   turned    (1)    by 
beating  down  the  plate  edge  with  hand  mauls,  while  the  plate  is 


THE  BOILER  SHOP 


347 


suitably  held  on  a  former  or  between  two  heavy  bars,  or  (2)  by  the 
hydraulic  flanging  machine.  Plates  are  usually  heated  to  a  bright 
red  along  the  edge  to  be  flanged.  Several  heats  may  be  necessary 
to  flange  the  edge  of  a  large  plate,  as  only  3  or  -1  feet  can  be  heated 
along  the  edge  at  one  time  and  flanged  before  undue  cooling. 

Flanged  plates  must  always  be  annealed  after  flanging  is  com- 
pleted as  the  flanging  heats  are  local  and  they  set  up  internal 


FIG.  228. — Flanging  Clamp. 

stresses  in  the  metal.  Large  plates  partly  or  wholly  flanged  may 
crack  if  left  to  cool  over  night  unannealed,  hence  it  is  well  to 
keep  plates  hot,  or  at  least  warm,  until  final  annealing  can  be  done. 
379.  Equipment  for  Flanging  by  Hand. — Fig.  228  shows  a 
flanging  clamp  for  holding  plates  for  straight  flanging.  Angle 
bars  of  various  curvatures  over  their  angles  are  furnished  for  plac- 
ing over  the  lower  clamp  to  give  the  desired  curvature  to  the 


FIG.  229.— Flanging  Former. 

flange.    When  the  plate  is  clamped,  the  flange  is  beaten  down  and 
finished  to  shape  by  hard-wood  mauls  and  other  hand  tools. 

Fig.  229  shows  a  cast-iron  former  F  made  for  flanging  special 
shapes.  The  sheet  to  be  flanged  must  be  held  down  either  by  bolts 
which  can  be  quickly  adjusted  or  by  some  other  means  such  as  the 
bar  B,  hook  H  and  iron  block  K.  The  hook  can  be  quickly  hooked 


348  MECHANICAL  PROCESSES 

under  the  edge  of  the  former,  and  the  block  is  pressed  securely  on 
the  plate. 

Heavy  hickory  mauls  are  used  to  beat  the  flange  down,  and  long- 
handled  flatters  and  fullers  are  used  to  shape  the  flange  exactly 
after  it  is  turned  by  the  mauls.  Sledges  must  be  used  with  caution 
if  at  all,  as  they  scar  the  flange  and  may  endanger  its  strength  or 
at  least  may  cause  a  bad  joint  between  the  scar  and  the  plate  on 
which  it  laps. 


FIG.  230. — Hydraulic  Flanging  Press. 

380.  The  Hydraulic  Flanging  Press. — This  machine  is  shown  in 
Fig.  230.  It  consists  of  a  heavy  cast-iron  body  carrying  four 
hydraulic  cylinders,  and  a  suitable  table  on  which  work  is  held 
steady  while  being  flanged. 

The  plunger  head  on  the  rod  A  of  the  outer  vertical  cylinder 
clamps  the  sheet  to  be  flanged  by  pressing  it  against  the  former- 
block  K.  The  head  on  the  rod  B  is  then  forced  down  against  the 
edge  of  the  plate,  turning  it  down  against  the  right-hand  edge  of 
the  former-block.  The  flat  end  F  on  the  rod  (7,  which  is  controlled 


THE  BOILER  SHOP  349 

by  the  horizontal  cylinder  partly  in  view,  is  then  forced  against 
the  flange  to  smooth  it.  The  triangular  block  G  serves  as  a  guide 
to  keep  B  in  place  as  it  descends. 

The  horizontal  cylinder  on  top  of  the  press  is  rigged  merely  to 
lift  the  heads  carried  by  the  vertical  cylinders.  The  pressure  in 
the  cylinders  A,  B  and  C  is  admitted  from  the  hydraulic  accumu- 
lator and  released  by  means  of  the  hand  levers  on  the  side  of  the 
press.  The  upper  cylinder  is  under  constant  pressure  and  acts 
similar  to  a  spring. 

When  the  edge  of  a  circular  plate  is  to  be  flanged,  a  heavy  cast- 
iron  pivot  is  bolted  to  the  center  of  the  plate  and  is  dropped  into  a 


fl 


FIG.  231. — Former  for  Hydraulic  Flanging. 

socket  on  an  extension  piece  bolted  to  the  table  of  the  press.  In 
this  way  the  turning  of  a  flange  truly  circular  is  assured. 

When  necessary  to  flange  the  edges  of  a  circular  or  an  elliptical 
hole  in  a  plate,  the  hollow  former-block  R  of  Fig.  231  is  bolted  to 
the  table  and  the  cross  head  Q  is  attached  to  both  vertical  cylinder 
rods  by  the  projections  K  and  M.  This  cross  head  carries  the 
hollow  flanging  block  P.  By  means  of  these  fittings  the  flange 
entirely  around  the  hole  is  pressed  at  one  motion. 

The  degree  of  heating  a  plate  edge  must  be  carefully  judged  so 
that  the  metal  will  be  pliable,  yet  not  soft  enough  to  be  torn  away 
by  the  downward  pull  of  the  flanging  head. 

381.  The  Hydraulic  Accumulator. — The  great  pressures  used  in 

hydraulic  machines  are  supplied  from  intensifies  on  the  principle 

of  that  shown  with  the  forging  press  in  a  previous  chapter,  or 

from  accumulators.    Water  in  an  accumulator  cylinder  is  subjected 

23 


350 


MECHANICAL  PROCESSES 


to  a  pressure  of  at  least  several  hundred  pounds  per  square  inch 
by  means,  of  weights  loaded  upon  the  cylinder  as  shown  in  Fig.  232. 
The  description  and  operation  of  the  accumulator  here  shown 
are  given  as  follows,  viz. :  A  heavy  base  B  rests  on  a  concrete 
foundation  and  supports  the  accumulator.  This  base  carries  a 
vertical  steel  rod  Et  called  the  ram,  and  short  vertical  supports  8 


FIG.  232. — Hydraulic  Accumulator. 

on  which  the  cylinder  rests  when  not  in  operation.  A  bronze 
sleeve  D,  about  !/o  or  %  of  an  inch  thick,  is  shrunk  over  the  lower 
end  of  the  ram.  The  ram  has  a  hole  along  its  axis  as  shown,  com- 
municating at  H  with  the  inside  of  the  heavy  cast-steel  cylinder  C. 
The  upper  end  of  the  ram,  which  acts  as  a  guide  for  the  cylinder  in 
its  variable  up  and  down  travel,  is  steadied  by  the  roof  trusses  of 
the  building  in  which  the  equipment  is  installed. 


THE  BOILER  SHOP 


351 


Water  is  forced  by  hydraulic  pumps  (steam-driven  pumps  with 
very  small  water  plungers)  through  the  pipe  G  and  the  opening  H 
into  the  space  W  between  the  rod  and  the  cylinder.  The  un- 
balanced pressure  on  the  end  of  the  bronze  sleeve  D  is  increased  by 
the  pumps  until  it  is  sufficient  to  raise  the  cylinder  and  the  weights 
which  it  carries.  These  annular  cast-iron  weights  determine  the 
degree  of  pressure  in  the  cylinder.  If  less  pressure  is  desired,  one 
or  more  of  the  weights  is  lifted  and  suspended  above  the  accumu- 
lator. 

This  pressure  is  used  by  transmitting  it  to  the  controlling  valves 
of  a  hydraulic  press  through  a  pipe  connected  at  K. 


FIG.  233. — Flange-Heating  Furnace. 

Suitable  automatic  controls  are  rigged  on  the  accumulator  to 
stop  the  pumps  when  the  cylinder  has  raised  its  full  height,  and  to 
prevent  a  sudden  drop  of  the  cylinder  in  case  a  pipe  should  sud- 
denly break. 

382.  Flange-Heating  Furnace. — Fig.  233  shows  a  hearth  or  fur- 
nace, partly  in  cross  section,  for  heating  the  edge  of  a  plate  for 
flanging.  It  is  a  brick-walled  basin  re-inforced  around  the  sides 
with  jron  plates  and  covered  with  perforated  plate  sections  as 
shown. 

The  furnace  is  operated  as  follows :  Supposing  a  curved  edge  of 
n  large  plate  is  to  be  flanged,  draw  a  chalk  line  BO  about  5  feet 
long,  representing  the  curve  of  the  flange.  The  perforations  along 


352  MECHANICAL  PROCESSES 

this  line  and  those  within  3  inches  on  each  side  of  it  are  left  open 
as  shown,  but  the  remainder,  over  the  entire  surface  of  the  plates, 
are  stopped  by  dropping  boiler  rivets  into  them.  Finely  broken 
soft  coal  free  from  sulphur  and  clinker  is  dampened  and  packed 
in  a  layer  about  8  or  10  inches  deep  over  the  rivet-covered  per- 
forations, leaving  the  open  perforations  about  BC  uncovered.  A 
fire  of  high-grade  soft  coal  or  preferably  coke,  is  built  along  BC 
over  the  open  perforations,  and  the  air  blast  is  turned  into  the 
hollow  space  beneath  the  plates.  The  air  is  free  to  escape  only 
through  the  fire  along  BC,  hence  the  fire  is  easily  confined  to  this 
space.  When  a  plate  edge  is  placed  over  this  strip  of  fire,  it  is 
covered  by  several  blocks  of  wood  and  old  pieces  of  sheet  iron 
which  confine  the  heat  and  facilitate  heating  the  plate. 

When  a  plate  is  flanged  along  two  edges  meeting  at  a  corner, 
the  corner  flanging  must  be  done  at  nearly  a  welding  heat.  The 
corner  is  rounded  off  before  flanging  to  remove  the  excess  of  metal. 

383.  Straightening  and  Annealing  of  Flanged  Plates. — The  work 
of  flanging  usually  warps  a  plate  more  or  less,  though  the  work  of 
straightening  can  frequently  be  done  before  it  goes  to  the  annealing 
furnace.     Flanged  plates  are  placed  in  a  large  coal  or  oil-burning 
furnace,  heated  red,  and  drawn  out  on  a  level  floor  of  cast-iron  slabs 
to  be  straightened  by  mauls  and  flatters. 

Annealing  also  takes  place  in  a  large  furnace.  The  annealing 
heat  is  best  gaged  by  a  pyrometer,  and  it  is  the  best  practice  to  allow 
plates  to  cool  gradually  in  the  furnace  by  shutting  off  the  fuel  supply. 

After  annealing,  flanged  plates  are  then  ready  for  marking  with 
the  location  of  rivet,  tube  and  stay-bolt  holes,  which  could  not  be 
marked  before  flanging,  as  a  slight  distortion  of  the  plate  would 
warp  these  marks  out  of  position. 

384.  Drilling  Holes  in  Boiler  Plates. — Eivet  and  other  holes  in 
boiler  plates  must  be  drilled  and  not  punched.     Holes  must  be 
carefully  located  on  the  plates  from  the  layout  diagrams.     Plates 
which  are  not  to  be  heated  for  flanging  or  other  purpose,  as  in  the 
case  of  shell  plates,  may  have  the  holes  drilled  as  soon  as  they  are 
laid  out.     It  is  well  to  bear  in  mind  that,  in  plate  edges  which 
lap,  rivet  holes  are  drilled  in  one  plate  according  to  the  lay-out 


THE  BOILER  SHOP  353 

diagram,  and  these  holes  serve  as  guides  for  drilling  the  lapping 
edge  of  the  other  plate.  When  two  plates  are  thus  drilled  in  con- 
tact, they  must  always  be  taken  apart  afterward  and  the  metal 
chips  and  burr  (rough  edge  of  the  hole)  removed,  otherwise  the 
joint  would  not  be  tight  after  riveting  together. 

The  principal  drilling  machines  of  the  boiler  shop  are  multiple 
and  portable  drills.  The  multiple  drill  (also  called  the  gang  drill) 
is  a  vertical-drilling  machine  with  several  drill  spindles  mounted 
at  adjustable  intervals  along  a  straight  carrying  bar.  Portable 
drills  are  either  pneumatic  or  electric  driven,  and  are  much  used 
for  drilling  holes  in  plates  after  the  parts  of  the  boiler  are  assembled 
and  temporarily  held  together  by  a  few  bolts.  Portable  drills  save 
shifting  the  position  of  heavy  boiler  parts  for  drilling.  The  ratchet 
drill,  for  drilling  by  hand,  is  useful  in  confined  spaces,  but  its 
work  is  slow. 

Holes  for  boiler  tubes,  usually  about  3  inches  in  diameter,  are 
drilled  in  the  tube  sheets  by  a  tube-hole  cutter,  which  cuts  a  disc 
of  metal  from  the  hole  instead  of  cutting  this  metal  out  in  fine 
chips. 

385.  Assembling  the  Parts  of  a  Boiler. — After  the  plates  com- 
posing a  boiler  have  been  trimmed  to  finished  dimensions,  rolled  to 
the  required  curvatures,  flanged,  and  have  had  enough  rivet  and 
other  holes  drilled  for  bolting  them  together  temporarily,  the  next 
step  is  to  assemble  them  into  correct  relative  position.  The  plates 
of  the  shell  are  first  assembled  in  rings  or  courses,  and  the  several 
courses  are  then  assembled  end  to  end;  the  combustion  chambers 
and  corrugated  furnaces,  which  are  placed  inside  a  cylindrical 
boiler,  are  assembled  complete  in  themselves,  and  when  they  are 
placed  inside  the  shell,  the  boiler  heads  are  placed  in  the  ends  of 
the  shell. 

As  each  group  of  plates  is  assembled,  rivet  holes  are  drilled  in 
the  lapped  edges  at  the  seams,  the  plates  are  taken  apart,  cleaned, 
re-assembled  and  finally  riveted  permanently  together. 

The  combustion  chambers  are  held  rigidly  in  place  in  the  boiler 
by  suitable  stay  bolts  which  fasten  them  to  the  shell,  or  fasten 
adjacent  chambers  to  each  other.  (See  Fig.  221.)  The  tubes  join  the 
combustion  chamber  to  the  boiler  head  and  serve  to  increase  the 


354 


MECHANICAL  PROCESSES 


rigidity  of  the  combustion  chamber  while  fulfilling  their  purpose  of 
conducting  gases  of  combustion  from  the  furnace  to  the  smoke  pipe. 
Tubes  are  placed  after  all  other  parts  are  assembled  and  riveted,  and 
after  the  screw  stays  are  placed. 


FIG.  234. — Hydraulic  Riveting  Machine. 

386.  Riveting. — Eiveting  is  done  by  (1)  hydraulic  riveting 
machines,  both  stationary  and  portable;  by  (2)  portable  pneumatic 
riveters,  and  by  (3)  hand  hammers.  Portable  hydraulic  riveters 
are  massive  and  must  be  carried  and  held  in  place  for  their  work 
by  a  crane. 


THE  BOILER  SHOP  355 

Fig.  234  shows  a  type  of  powerful  stationary  hydraulic  riveter. 
This  is  used  to  rivet  the  shell  plates  together  and  to  rivet  one  head 
in  the  shell.  The  shell  is  suspended,  with  its  axis  vertical,  by 
chains  attached  to  a  crane  which  is  a  part  of  the  equipment  of  this 
machine.  The  riveting  dies,  closed  together  in  the  view,  are  opened 
to  allow  work  to  be  suspended  in  the  gap  between  the  two  arms  of 
the  machine,  the  arm  on  the  right  projecting  up  inside  the  shell. 
The  die  is  placed  as  high  on  the  right  arm  as  possible  to  allow  it  to 
be  used  in  riveting  boiler  heads  and  other  flanged  work.  The 
hydraulic  cylinder  is  so  arranged  that  three  different  pressures, 
50,  100  and  150  tons,  may  be  exerted  on  rivets  of  various  sizes. 
The  men  who  operate  the  machine  stand  on  a  platform,  not  shown, 
built  near  the  top  of  the  arms.  Heated  rivets  are  passed  up  from 
a  small  furnace  at  the  base  of  the  machine. 


JB 

FIG.  235. 

Portable  pneumatic  riveters  are  much  used  for  bridge,  ship  and 
boiler  work.  They  are  held  in  the  hands  of  the  workman  and  may 
be  operated  in  confined  spaces  too  small  even  for  driving  rivets  with 
hammers.  These  machines  are  supplied  by  air  at  a  pressure  of 
about  60  pounds  per  square  inch,  led  through  a  hose  from  an  air 
compressor.  Eivets  are  held  in  place  while  driving  by  a  man  or  boy 
who  presses  a  sledge  hammer  or  other  mass  of  iron,  suitably  sup- 
ported, against  the  rivet  head.  Pneumatic  holders-on  are  also  used 
for  this  purpose. 

Careless  or  fraudulent  work  in  laying  off  and  drilling  rivet  holes 
will  bring  about  a  lack  of  coincidence  of  two  holes  as  shown  at  B  in 
Fig.  235.  If  the  relative  displacement  is  slight,  it  may  be  remedied 
by  careful  re-drilling  or  by  reaming.  A  bad  practice  is  to  drive  a 
tapered  steel  pin  into  the  hole  to  enlarge  it  (called  "drifting"), 
and  then  to  put  in  a  small-bodied  rivet  to  cover  up  the  defect. 


356  MECHANICAL  PROCESSES 

387.  Rivet-Heating  Furnace.— Bivets  are  heated  preparatory  for 
driving  in  a  forge,  or  more  efficiently  in  a  small  oil-burning  furnace, 
a  type  of  which  is  shown  in  Fig.  236.  This  consists  of  a  small  sheet- 
steel  box,  lined  with  fire  brick,  mounted  on  its  fuel  tank.  Through  the 
small  hole  in  the  end  of  the  furnace  an  atomizer  sprays  oil  into  the 
flame  which  is  maintained  by  the  burning  of  this  spray.  The 
atomizer,  or  burner,  is  connected  to  its  fuel  tank  and  to  a  com- 


FIG.  236.— Rivet  Heater. 

pressed  air  tank  which  supplies  furnaces  with  air  at  a  moderate 
pressure. 

388.  Methods  of  Holding  Boiler  Tubes  in  Place.— Fig.  237  shows 
the  method  of  holding  tubes  in  a  shell  boiler.  The  ends  of  an 
ordinary  tube  are  expanded  to  fit  tightly  against  the  sides  of  the 
holes  in  the  tube  sheets.  The  stay  tubes,  heavier  than  ordinary 
tubes,  are  screwed  into  the  tube  sheets.  Stay  tubes  are  spaced  at 
intervals  among  the  ordinary  tubes  to  brace  the  tube  sheets  rigidly. 


THE  BOILER  SHOP 


357 


It  is  frequently  the  practice  to  flare  or  bead  over  the  tube  ends  to 
insure  tight  joints. 

Tubes  of  water-tube  boilers  are  usually  expanded  into  their 
headers.  Very  few  water-tube  boilers  have  screw  tubes. 


•J* 


FIG.  237. — Method  of  Fastening  Boiler  Tubes. 

Fig.  238  shows  a  tube  expander  for  expanding  tube  ends.  This 
consists  of  a  sleeve  S  carrying  three  hard-steel  rollers  R  in  loose 
bearings,  a  cap  C,  and  a  tapered-steel  pin  P.  The  sleeve  is  placed 
in  the  end  of  the  tube  far  enough  to  bring  the  edge  of  the  cap 


FIG.  238. — Tube  Expander. 

against  the  tube  sheet.  The  steel  pin  is  driven  in  fairly  tight, 
and  is  revolved  by  a  small  steel  rod  placed  through  one  of  the  holes 
at  the  end.  The  pin  presses  against  the  inner  edges  of  the  rollers 
R,  and  as  the  pin  revolves  it  turns  the  rollers  around  against  the 


358  MECHANICAL  PROCESSES 

inside  of  the  tube,  expanding  the  end  tightly  against  the  hole  in 
the  sheet. 

Beading  is  done  by  a  beading  tool,  shown  in  Fig.  239.  This 
tool  may  be  struck  by  a  hammer  or  operated  by  a  pneumatic  holder 
such  as  is  used  in  chipping  or  riveting. 


FIG.  239.— Beading  Tool. 

389.  Chipping  and  Caulking.— After  the  riveting  of  a  boiler  is 
completed,  the  various  lapped  seams  are  made  tight  by  caulking 
the  beveled  edges  of  the  sheets.  A  flanged  joint  is  usually  made, 
as  shown  in  Fig.  240,  with  the  lap  of  the  end  D  on  the  outer  face 
of  the  flange  and  not  on  the  inner  face  B  except  for  a  particular 
reason. 

This  arrangement  enables  the  beveled  edge  of  each  sheet  to  be 
set  down  against  the  adjacent  surface  tightly,  as  shown  at  KK. 


FIG.  240.— Example  of  Caulking. 

This  operation  of  caulking  is  preceded  by  cutting  the  edge  of  the 
plate  to  a  uniform  bevel.  Flat-plate  edges  may  be  beveled  by 
planing,  though  edges  of  curved  flange  plates  are  beveled  by  chip- 
ping with  the  cold  chisel  driven  by  the  hammer  or  better  by  the 
pneumatic  holder.  Chipping  may  be  done  before  or  after  the  joint  is 
riveted,  and,  if  done  after  riveting,  great  care  must  be  taken  to  avoid 
gashing  the  surface  of  the  adjacent  plate. 

A  caulking  tool  is  virtually  a  cold  chisel  with  a  blunt  end.    Two 
styles  of  caulking-tool  ends  are  shown  at  E  and  8  in  Fig.  240. 


THE  BOILER  SHOP  359 

390.  Corrugated  Furnaces. — The  locomotive  type  of  boiler  has  a 
square  fire  box  at  one  end,  but  the  cylindrical  type  of  marine-shell 
boiler  is  fitted  with  one  or  more  corrugated  furnaces  such  as  is 
shown  in  Fig.  221.     These  furnaces  are  divided  along  the  center 
by  the  grate  bars,  and  they  are  corrugated  to  enable  them  to  resist 
the  collapsing  pressure  of  the  water  which  surrounds  them  in  the 
boiler.     Each  furnace  is  usually  about  40  inches  in  diameter  and 
7  feet  long. 

These  furnaces  are  made  in  the  United  States  only  by  The  Con- 
tinental Iron  Works  of  Brooklyn,  New  York.  Briefly,  the  process 
of  making  a  furnace  is  as  follows :  A  mild  steel  plate  from  the 
rolling  mill  is  bent  into  a  cylinder  in  the  bending  rolls.  The  two 
edges  are  lap-welded  by  passing  the  lap,  at  a  welding  heat,  between 
two  disc  rollers  pressed  against  the  seam  by  hydraulic  pressure. 
After  welding,  the  cylinder  is  heated  to  a  bright  red  heat  in  a 
furnace.  It  is  then  lifted  by  the  crane  and  carried  to  the  corru- 
gating machine,  the  vertical  rolls  of  which  are  suitably  shaped  to 
press  the  corrugations  gradually  on  the  cylinder  as  it  revolves 
repeatedly  between  the  rolls.  After  the  corrugations  are  pressed, 
the  end  is  heated  and  flanged  to  the  shape  required,  and  the  whole 
furnace  is  then  annealed. 

These  furnaces  are  always  made  to  order. 

391.  Other  Equipment  for  the  Boiler  Shop. — Besides  the  equip- 
ment so  far  named  for  this  shop,  the  shop  should  have 

(1)  Power  shears  for  shearing  heavy  steel  plates  up  to  about 
1%  inches  thick. 

(2)  Power  punch  for  punching  holes  in  plates  up  to  about  li/> 
inches  thick.    This  punch  is  not  used  for  punching  rivet  holes  un- 
less they  are  afterward  enlarged  by  drilling. 

(3)  Hand  shears  and  punch,  either  in  two  machines  or  com- 
bined in  one  machine,  for  shearing  and  punching  holes  in  plates 
of  %-inch  thickness  or  less. 

(4)  Hand  pump  of  simple  design  for  testing  new  boilers  under 
hydrostatic  pressure. 

(5)  Cranes  and  other  lifting  appliances  such  as  are  installed  in 
the  machine  shop. 


360 


MECHANICAL  PROCESSES 


FIG.  241,— Vertical  Power  Punch. 


FIG.  242. — Vertical  Power  Shears. 


THE  BOILER  SHOP  361 

392.  Power  Shears  and  Punch. — One  type  of  these  machines  is 
shown  in  Figs.  241  and  242.  Plates  are  held  flat  for  shearing  or 
punching  in  chain  slings  carried  on  the  hook  of  the  crane.  Two 
men  usually  hold  the  plate  to  guide  it  under  the  machine  at  the 
direction  of  a  third  man  who  sets  the  machine  in  motion  by  means 
of  a  conveniently  placed  foot  or  hand-lever. 

Punch  and  shears  are  often  in  one  double  machine,  or,  by  a 
change  of  equipment,  a  punch  may  be  changed  for  shearing,  or 
vice  versa. 


FIG.  243. — Hand  Shears  and  Punch. 

That  part  of  a  plate  operated  on  by  punch  or  shears  is  necessarily 
strained  to  a  point  of  disruption.  Metal  on  each  side  of  a  shearing 
line  or  around  a  punched  hole  is  strained  more  or  less  according  to 
its  proximity  to  the  line  of  disruption,  and  some  of  this  metal  is 
strained  beyond  its  elastic  limit,  and  hence  is  less  strong  than  it 
was  before.  For  this  reason,  when  boiler  plates  are  punched  or 
sheared,  a  punched  hole  must  be  drilled  larger,  and  the  sheared  edge 
must  be  planed  or  chipped  away  sufficient  to  remove  the  metal 
strained  beyond  the  elastic  limit. 

393.  Hand  Shears  and  Punch. — Fig.  243  shows  a  convenient 
form  of  this  machine.  It  may  be  bolted  to  a  heavy  bench  or  set  on 


362  MECHANICAL  PROCESSES 

a  portable  stand.    Small  punches  are  frequently  fitted  to  be  operated 
by  hydraulic  pressure. 

394.  Shapes   of   Rivets. — Fig.   244   shows   the   usual   shapes   of 


/        2       y 

FIG.  244. — Types  of  Rivel  Heads. 

rivets  for  ship,  bridge,  boiler  and  tank  work.     They  are  designated 
as  follows : 

(1)  Pan  head.  (3)   Countersunk. 

(2)  Button  or  round  head.  (4)    Cone  or  boiler  head. 

Rivet  lengths  do  not  include  the  head,  except  in  the  case  of  the 
countersunk  rivet. 


CHAPTER  XIII. 
OTHER  SHOPS— SPECIAL  PROCESSES. 

395.  Sheet  Metal  Work     -This  is  a   subsidiary  work  in  large 
building  plants.    It  consists  of  making  tanks,  casings,  large  copper 
pipes,  fenders,  wheel  guards,  smoke  and  other  conduits,   and  re- 
ceptacles for   oils  and   other  materials.     The  heavier   sheet-metal 
work  is  done  in  the  boiler  shop,  where  it  is  shaped  by  the  equipment 
of  that  shop.    The  lighter  sheet-metal  work  is  shaped  by  hand  ap- 
pliances in  the  copper  shop  or  sometimes  in  a  separate  sheet-metal 
shop. 

Sheet  metals  are  fastened  together  by  riveting,  soldering,  or 
brazing.  Seams  in  wrought  iron  or  mild  steel  sheet  work  of  moder- 
ate thickness  may  be  readily  and  effectively  welded  by  the  oxy- 
acetylene  blowpipe.  Wiping  a  joint  in  plumbing  work  and  sweat- 
ing-on  are  forms  of  soldering. 

By  far  the  greater  part  of  sheet-metal  work  is  done  in  re-manu- 
facturing processes  such  as  were  described  in  Chapter  Y.  In  plants 
which  do  this  kind  of  work,  large  quantities  of  a  particular  article 
are  made  at  minimum  expense,  and  only  special  articles  of  certain 
shapes  needed  in  small  quantities  are  shaped  by  the  expensive 
manual  operations  of  the  sheet-metal  shop  in  a  general  building 
plant. 

396.  The  Copper  Shop.    Materials  Used. — There  is  usually  con- 
siderable copper-pipe  work  to  be  done  in  a  ship  or  engine-building 
plant.    This  is  the  principal  work  of  the  copper  shop. 

Copper  is  much  used  for  small  and  medium-sized  steam  pipes 
which  are  subjected  to  moderate  pressures,  and  for  pipes  to  convey 
salt  water  and  other  liquids.  This  material  is  easily  worked,  is 
non-corrosive  for  all  ordinary  uses,  and  is  particularly  adopted  for 
pipes  which  must  have  many  crooks  and  bends  to  fit  in  confined 
spaces.  Copper  pipes  often  suffer  in  marine  use  from  galvanic 
action,  and  tinning  is  much  resorted  to  for  protecting  them. 

The  larger  sizes  of  pipes  are  made  of  sheets  of  medium-hard 
rolled  copper  bent  to  cylindrical  shape  and  brazed  along  the  scarfed 


364  MECHANICAL  PROCESSES 

edges.  Copper  pipe  up  to  8  inches  in  diameter  is  made  from  seam- 
less-drawn copper  tubing  supplied  from  the  tube  mill.  An  assort- 
ment of  this  tubing  is  carried  in  stock  in  the  copper  shop. 

Sheet  copper  comes  from  the  rolling  mill  either  thoroughly  an- 
nealed as  dead  soft  sheets  dull  in  color,  or  of  many  degrees  of 
hardness  and  springiness  due  to  the  pressure  exerted  by  the  rolls 
and  to  greater  or  less  annealing  after  rolling.  Planished  sheet  copper 
has  a  bright  polished  surface  as  a  result  of  rolling  without  subsequent 
annealing. 


FIG.  245. — Bench  Shears. 

The  stock  of  material  in  the  copper  shop  also  includes  more  or 
less  sheet  brass  of  different  thicknesses,  degrees  of  hardness  due  to 
rolling,  and  of  a  composition  suitable  for  shaping  by  bending  and 
hammering  cold. 

397.  Copper  Shop  Equipment. — This  shop  is  equipped  with 
various  hand  appliances  for  cutting,  bending,  hammering  and  rivet- 
ing tubes  and  sheet  metals;  with  small  furnaces  for  brazing  and 
annealing;  and  with  apparatus  for  soldering. 


FIG.  246. — Snips. 

The  shop  equipment  also  includes,  as  does  that  of  most  other 
shops,  squares,  measuring  rules,  files,  vises,  compasses,  cold  chisels, 
metal  saw,  hand  punches,  wood  mallets  and  scribers. 

398.  Cutting,  Bending  and  Riveting  Tools. — The  principal  tools 
for  these  uses  are  as  follows : 

(1)  Bench  shears.     These  are  used  for  heavier  cutting  and  are 
supported  while  in  use  by  placing  the  bend  of  the  lower  handle  in 
a  square  hole  in  the  bench.    See  Fig.  245. 

(2)  Snips,  or  hand  shears.    Fig,  246. 

(3)  Forming  machine.    This  is  a  small  set  of  bending  rolls  used 
for  bending  sheets  into  cylindrical  form  as  described  in  boiler-shop 


OTHER  SHOPS — SPECIAL  PROCESSES 


365 


work.  These  rolls  are  seldom  longer  than  3  feet,  hence  for  bending 
longer  sheets,  a  bending  block  is  used,  the  end  view  of  which  is 
shown  in  Fig.  247.  The  solid  iron  mandrel  B  bends  the  sheet  and 
the  projecting  edges  are  then  beaten  over  it  with  wood  mallets. 


FIG.  247.— Bending  Block. 


(4)  Tinners'    stakes.      These    tools    are   anvils   for   sheet-metal 
workers.     Fig.  248  shows  a  few  of  the  many  designs.     They  are 
supported  in  a  square  hole  in  the  bench. 

(5)  Mandrels.     These  are  long  round  bars  of  iron.     One  end  is 
clamped  down  against  the  back  edge  of  the  bench  top  and  the  other 


FIG.  248. — Tinners'  Stakes. 

end  projects  out  horizontally  two  or  more  feet  beyond  the  bench 
for  use  as  an  anvil  in  shaping  work. 

(6)   Expanders.  These  are  very  similar  to  a  boiler-tube  expander. 

They  are  used  to  expand  a  copper  pipe  slightly  for  about  3  inches 

from  the  end  for  fitting  two  pipes  together  in  a  cup  joint.     An 

efficient  expander  may  be  easily  made  of  a  sleeve  coupling  (pipe- 

24 


366 


MECHANICAL  PROCESSES 


fitting)   screwed  on  the  end  of  a  short  piece  of  iron  pipe.     This 
coupling  is  driven  into  the  end  of  the  pipe  to  be  expanded. 

(7)  Drift  set.     This  tool  is  shown  in  Fig.  249,  No.  3,  and  is 
used  to  set  the  metal  of  the  fillet  d,  Fig.  256,  against  the  inner  pipe 
to  make  a  close-fitting  joint  preparatory  to  brazing  the  joint. 

(8)  Collar  lifters.     These  tools   (Nos.  1  and  2,  Fig.  249)   are 
used  to  enlarge  a  small  hole  drilled  through  the  wall  of  a  copper 


FIG.  249. — Coppersmith  Tools. 

pipe  as  an  opening  for  a,  branch  outlet.    Their  use  is  shown  in  Fig. 
257. 

(9)  Burring  machine.  This  machine  is  placed  on  the  bench 
and  operated  by  a  crank.  Its  small  disc  rollers  or  "  faces  "  turn  a 
burr  or  flange  on  the  end  of  a  thin  hollow  cylinder,  as  a  can  end, 
and  on  the  edge  of  a  disc  of  metal  to  form  a  bottom. 


||i'"Mi'     -| 
FIG.  250. — Rivet  Set. 

(10)  Beading  machine.     This  is  another  small  portable  bench 
machine.    It  rolls  different  designs  of  corrugations  around  the  body 
of  a  pipe  near  the  open  end.    These  corrugations,  are  usually  seen 
as  fancy  rings  on  stove  pipes  or  sheet-metal  utensils,  and  they  serve 
the  purpose  of  stiffening  the  walls  of  the  pipe. 

(11)  Rivet,  set.     This  set  is  used  as  shown  in  Fig.  250.     The 
edges  of  two  sheets  of  metal  &  and  c  are  placed  over  the  rivet  as 


OTHER  SHOPS — SPECIAL  PROCESSES 


367 


shown.  The  set  D  is  so  placed  that  when  struck  with  a  hammer  the 
rivet  will  punch  a  hole  through  the  metal.  The  set  is  then  shifted 
to  place  the  small  cone-head  depression  over  the  rivet  end,  and  a 
hlow  of  the  hammer  sets  the  end  down  to  the  form  of  the  de- 
pression. 

(12)    Pipe  bender.     This  machine  is  made  in  many  forms  by 
different  makers.    Fig.  251  shows  a  diagram  of  a  machine  adapted 


FIG.  251. — Pipe-Bending  Machine. 

to  cold  bending  of  wrought  iron  or  other  pipes  up  to  2-inch  diam- 
eter when  using  steam  or  compressed  air.  A  hydraulic  machine 
can  bend  larger  pipes.  A  die  B  is  carried  on  the  end  of  a  piston 
rod  C,  and  another  die  D  rests  solidly  on  the  frame  of  the  machine. 
The  pipe  is  slowly  bent  as  B  travels  toward  D.  The  grooves  in 
B  and  D  must  exactly  fit  the  size  of  pipe  to  be  bent  to  keep  the  pipe 
from  flattening  out  of  round  as  it  bends. 


23*?- 
FIG.  252. — Coppersmith  Hammers. 

399.  Coppersmith  Hammers. — Fig.  252  shows  the  hammers  made 
especially  for  coppersmiths'  use.  Their  designations  and  uses  are 
as  follows: 

(1)  Eaising  hammer.    Used  to  cup  flat  work. 

(2)  Planishing  hammer.     This  has  polished  faces  and  is  used 
to  smooth  the  marks  and  wrinkles  formed  on  pipes  and  other  work 
during  the  operation  of  making  them  by  hand. 


368  MECHANICAL  PROCESSES 

(3)  Collar  hammer.     Used  to  chamfer  the  edge  of  a  sheet  for 
making  a  lap  joint,  or  for  bell  mouthing  the  end  of  a  pipe. 

(4)  Spanking  hammer.    Used  to  smooth  the  surface  of  a  straight 
pipe  as  it  rests  over  a  mandrel. 

400.  Brazing, — This  is  a  process  much  used  for  uniting  copper, 
brass  or  iron  in  a  solid  metallic  joint  of  considerable   strength, 
though  the  strength  of  the  joint  is  not  equal  to  that  of  the  solid 
metal.     The  brazing  material  used,  known  as  hard  solder,  spelter, 
or  brazing  metal,  is  variable  in  its.  composition.     It  may  contain 
copper,  zinc,  tin,  and  silver,  according  to  the  melting  point  required 
and  to  the  required  strength  of  joint.     The  usual  composition  for 
brazing  brass  and  copper  is  about  60%  copper  and  40%  zinc.    This 
alloy  is  melted  together,  and,  after  cooling  it  is  heated  to  redness 
and  broken  into  small  lumps  in  a  heavy  mortar  or  on  the  anvil. 

The  essentials  in  brazing  are  (1)  the  metals  to  be  brazed  must 
be  filed  or  scraped  to  a  clean  metallic  surface  and  must  be  pro- 
tected from  becoming  re-coated  with  oxide  during  the  process  by 
means  of  a  flux,  and  (2)  the  metals  to  be  joined  together  must 
have  higher  points  of  fusion  than  that  of  the  brazing  metal. 

Brazing  is  accomplished  by  applying  a  considerable  degree  of 
heat  to  the  parts  to  be  brazed.  This  heat  melts  the  brazing  metal 
and  allows  it  to  run  into  the  joint.  The  two  parts  to  be  brazed 
must  be  suitably  held  together  by  wires,  tongs  or  clamps  and  the 
brazing  metal  must  be  so  placed  on  the  joint  that  gravity  will  cause 
it  to  flow  into  all  parts  of  the  joint  when  melted. 

Borax,  fused  to  drive  off  the  water  of  crystalization  and  powdered 
wrhen  cold  for  applying  it  easily,  is  used  as  a  flux.  It  may  be  mixed 
with  the  broken-up  brazing  metal  if  desired.  If  water  of  c^stali- 
zation  is  not  driven  off,  the  borax  swells  and  bubbles,  causing  more  or 
less  annoyance. 

401.  Heat  for  Brazing. — The  necessary  heat  for  brazing  is  usually 
supplied  by  a  flat-topped  forge  or  brazing  table  such  as  is  shown  in 
Fig.  253.    This  forge  uses  gas  or  oil  fuel  forced  into  the  flame  by 
compressed  air.     The  air  is  necessary  for  the  complete  burning  of 
the  fuel  to  avoid  a  soot  deposit  on  the  work. 

A  forge  table,  similar  to  that  shown,  but  with  air-blast  connec- 
tion as  in  the  blacksmith's  forge,  is  much  used  for  charcoal  or  coke 
fuel.  This  gives  a  less  intense  heat  than  gas  or  oil  and  is  preferred 


OTHER  SHOPS — SPECIAL  PROCESSES  369 

by  many  workmen  for  lighter  brazing  work.  A  blacksmith's  forge 
with  charcoal  or  coke  fuel  may  be  used  for  brazing. 

A  compound  blowpipe  with  rubber-hose  connections  to  gas  and 
compressed-air  supply  is  used  as  a  portable  heater  where  work  can- 
not be  brought  to  the  furnace. 

Small  articles  may  be  brazed  by  means  of  the  mouth  blow  pipe, 
or  mav  be  heated  in  a  charcoal  fire  without  air  blast. 


FIG.  253. — Brazing  Forge. 

Some  compositions  of  brass  are  difficult  to  braze  because  the  zinc 
in  them  tends  to  melt  out.  Also  they  are  usually  very  brittle  when 
hot  and  must  be  handled  carefully  and  allowed  to  rest  quietly* 
and  free  from  air  drafts  until  cool. 

402.  Annealing. — Copper  and  brass  sheets  are  frequently  shaped 
by  hammering  cold,  as  in  shaping  a  hemispherical  or  other  concave 
receptacle  from  a  flat  sheet,  or  in  making  bent  copper  pipes.  The 
metal  becomes  more  or  less  hard  and  brittle  by  hammering,  and 
continued  working  would  cause  it  to  crack.  At  intervals  during 


370 


MECHANICAL  PROCESSES 


the  shaping,  when  the  metal  gets  hard  enough  to  produce  a  metallic 
ring,  it  must  be  annealed.  This  is  done  by  heating  it  evenly  on 
the  brazing  furnace  and  allowing  it  to  cool.  Copper  may  be  cooled 
quickly  by  holding  it  in  an  air  draft  or  plunging  it  into  water,  but 
it  is  safest  to  anneal  brass  of  properties  not  thoroughly  known  by 
letting  it  cool  slowly  where  it  is  free  from  air  drafts. 

403.  Soldering. — This  process  of  joining  metals  is  much  used  by 
tinners  and  other  sheet-metal  workers  for  joints  requiring  but 
moderate  strength.  It  is  a  simpler  and  more  convenient  process 
then  brazing,  as  solder  melts  at  a  low  temperature. 

A  soldering  outfit  consists  of  the  following-named  items : 
(1)   Soldering  irons    (more  correctly  called  soldering  coppers) 
as  shown  in  Fig.  254.    The  lower  copper  is  for  heavy  work. 


FIG.  254. — Soldering  Coppers. 

(2)  Heater  for  soldering  irons.     This  consists  either  of  a  small 
sheet-iron  fire  pot  in  which  a  fire  of  coke  or  charcoal  is  kept,  or  a 
gasoline  torch  with  an  attached  rack  for  supporting  the  coppers  in 
reach  of  the  flame. 

(3)  Lead  pans  or  cups  for  holding  flux  and  acid  to  assist  in 
soldering. 

Solder,  like  spelter,  varies  in  the  proportions  of  its  constituents 
according  to  the  degree  of  hardness  required,  but  the  usual  com- 
position is  1  part  lead  and  1  part  tin  for  tinners'  work,  or  2  parts 
lead  and  1  part  tin  for  plumbers'  work.  The  ingredients  of  solders 
and  spelters  must  be  pure.  Tinners'  and  plumbers'  solder  is 
designated  as  soft  solder  to  distinguish  it  from  hard  solder  for 
brazing. 

404.  Method  of  Soldering. — Two  pieces  of  metal  to  be  soldered  to- 
gether must  be  filed  or  scraped  to  a  clean  metallic  surface  if  not 


OTHER  SHOPS — SPECIAL  PROCESSES  371 

already  bright.  They  are  brought  into  the  position  in  which  they 
are  to  be  soldered  and  firmly  held  together.  The  joint  is  sprinkled 
or  swabbed  with  flux  to  remove  grease  and  prevent  the  formation  of 
oxide.  Holding  a  bar  of  solder  in  one  hand  and  a  heated  soldering 
copper  in  the  other,  the  operator  brings  the  copper  against  the  bar, 
melting  a  slight  amount  of  solder  which  either  drips  on  the  joint  or 
sticks  to  the  point  of  the  copper  by  which  it  is  wiped  and  spread 
over  the  joint.  The  two  parts  to  be  joined  must  be  heated  by  the 
copper  to  the  fusion  point  of  the  solder  in  order  to  make  the  molten 
solder  stick  to  them. 

A  stronger  joint  may  be  made  by  first  carefully  tinning  the  sur- 
faces joined  in  soldering. 

The  end  of  a  soldering  copper  must  be  kept  filed  to  a  smooth 
point  and  this  point  is  tinned  with  solder  by  rubbing  it  on  a  stick 
of  solder.  In  heating  the  copper  for  use,  it  should  not  be  heated 
enough  to  melt  the  solder  from  the  point. 

Soldering  coppers  heated  by  the  electric  current  from  an  ordinary 
lamp  socket  are  very  convenient,  dispensing  witli  the  use  of  the 
fire-pot. 

Soldering  fluxes  remove  grease  and  dirt,  and  assist  in  reducing 
or  fusing  the  film  of  oxide  covering  the  work.  The  usual  fluxes 
are  rosin,  sal  ammoniac,  zinc  chloride,  and  borax. 

405.  Copper  Pipe. — This  pipe  is  often  made  by  the  coppersmith 
from  sheet  copper,  but  it  is  better  and  cheaper  to  use  lengths  of 
seamless  drawn  pipe  from  the  tube  mill.  The  mill  supplies  pipe  up  to 
8  inches,  or  possibly  10  inches  in  diameter.  Larger  pipes  must  be 
made  from  sheet  copper. 

A  great  advantage  in  the  use  of  pipes  made  of  copper  is  the 
safety  and  ease  with  which  such  pipes  may  be  bent  to  suit  the  many 
crooks  and  turns  necessitated  by  cramped  machinery  spaces.  Thin- 
walled  pipes  (about  No.  12  gage  or  thinner)  are  filled  with  melted 
rosin  and  heavier  pipes  are  filled  with  dried  sand  to  keep  them  from 
flattening  when  bent.  A  wood  plug  is  driven  in  one  end  of  the 
pipe,  the  entire  length  is  filled  with  rosin  or  sand,  and  another  plug 
is  driven  tightly  in  the  other  end.  Eosin-filled  pipes  are  bent  cold 
and  sand- filled  pipes  are  bent  hot.  Bending  is  done  in  the  hydraulic 
bending  press,  or  by  holding  one  end  between  two  pegs  or  clamps 


37.2 


MECHANICAL  PROCESSES 


and  pulling  the  other  end  with  a  block  and  tackle.  A  length  of 
pipe  may  be  slipped  over  each  end  of  the  pipe  to  be  bent  to  assist 
in  holding  and  in  increasing  the  leverage  of  the  pulling  force. 

Bending  causes  kinks  or  wrinkles  to  form  at  the  inner  curvature 
Dr  throat  of  the  pipe.  These  must  be  carefully  hammered  smooth 
while  the  pipe  remains  filled.  The  copper  along  the  outer  surface 
of  curvature,  or  back,  of  the  bend  is  necessarily  thinned  somewhat 
in  bending,  hence  the  practice  of  selecting  a  pipe  with  walls,  two  or 
more  gages  thicker  than  is  otherwise  required. 

Large  pipes,  or  those  of  any  size  bent  to  a  curve  of  small  radius, 
are,  in  high-grade  work,  bent  in  two  stages,  {.  e.,  the  pipe  is  filled 


FIG.  255. 

Copper  Pipe  Joints. 


FIG.  256. 


and  bent  part  way  to  the  required  radius,  is  emptied,  annealed, 
refilled  and  bent  to  the  full  extent  required. 

Small  pipes  may  be  bent,  when  filled,  by  means  of  the  grooved 
formers  shown  in  Fig.  251. 

406.  Joining  Lengths  of  Copper  Pipe. — One  length  of  pipe  may  be 
joined  to  another  by  composition  flanges  as  shown  in  Fig.  255  or 
in  a  permanently  brazed  cup  joint  as  shown  in  Fig.  256. 

The  flange  joint  may  be  readily  taken  apart  by  removing  the 
bolts.  Flanges  are  standardized  in  all  their  dimensions  and  in  com- 
position. Each  length  of  pipe  is  permanently  connected  to  its 
flange  by  beading  at  the  end,  as  at  l>,  into  a  recess  in  the  flange, 
and  by  brazing  around  the  groove  c  made  for  holding  the  brazing 


OTHER  SHOPS — SPECIAL  PROCESSES  373 

metal  after  it  melts.  A  flange  is  brazed  on  while  the  pipe  rests 
vertically,  and  frequently  a  ring  of  plastic  fire  clay  is  built  around 
the  joint  on  the  flange  shoulder  d  to  keep  the  brazing  metal  on  the 
joint  while  molten. 

The  lap  of  a  cup  joint  is  about  equal  to  the  diameter  of  the  pipe. 
The  cupped  portion  b  is  expanded  by  an  expander,  the  bell-mouth  c 
is  flared  by  the  collar  hammer,  and  when  the  two  lengths  of  pipe 
are  cleaned  for  brazing  and  fitted  together,  the  fillet  d  is  closed 
against  the  inner  pipe  by  the  drift  set.  After  brazing,  the  joint 
is  smoothed  by  filing.  The  flared  ring  c  assists  to  stiffen  the  pipe. 


FIG.  257. — Preparing  a  Branch  Joint  Opening. 

407.  Brazing-  a  Branch  in  a  Copper  Pipe. — To  connect  a  branch  to 
a  length  of  pipe  B,  Fig.  257,  drill  a  hole  about  f-inch  in  diameter 
in  the  pipe.  Beginning  with  the  small  collar  lifter,  lift  the  edges 
of  the  hole  carefully  and  evenly  all  around  by  strokes  of  the 
hammer  on  the  under  side  of  the  lifter.  When  the  hole  is  increased 
an  inch  or  more  in  diameter,  the  larger  lifter  may  be  used.  Care 
must  be  taken  not  to  crack  the  metal  by  excessive  expanding  with- 
out annealing,  nor  by  too  much  hammering  at  one  place.  When  a 
collar  is  raised  as  shown  at  C,  the  edge  is  flared  and  a  cup  joint  is 
formed  for  brazing. 

Another  type  of  branch  joint  may  be  made  by  cutting  a  hole  in 
the  pipe  nearly  the  size  of  the  desired  outlet,  lifting  the  edge  as  a 
slight  collar,  and  placing  over  the  outside  of  this  collar  the  end  of 
the  branch.  This  end  is  suitably  flared  to  lie  snugly  against  the 


374  MECHANICAL  PROCESSES 

outer  surface  of  the  pipe  which  it  joins,  forming  a  saddle  flange 
which  is  brazed  to  the  pipe. 

A  hole  in  a  copper  pipe  may  be  stopped  by  brazing  on  a  flush 
patch,  which  lies  flush  with  the  surface  of  the  pipe,  or  by  brazing 
on  an  exposed  patch,  which  overlaps  the  outer  surface  of  the  pipe. 

408.  The  Plate  and  Angle  Shop. — Plates  and  structural  shapes  of 
mild  steel  used  in  ship  building  are  cut  and  bent  to  shape  in  this 
shop,  the  principal  equipment  of  which  consists  of.: 

(1)  Power  punches,  used  principally  for  punching  rivet  holes 
in  ships'  plates  and  frames. 

(2)  Power  shears  for  trimming  edges  of  plates,  and  for  cutting 
lengths  of  angles,  beams  and  other  structural  shapes. 

(3)  Plate-edge  planer. 

(4)  Bending  rolls. 

(5)  Garboard  bending  press  (hydraulic)  for  bending  plates  cold 
to  other  than  cylindrical  form. 

(6)  Beam  and  angle  bending  or  straightening  machine. 

(7)  Bending  slab  and  heating  furnace. 

Machines  mentioned  in  items  1  to  4  inclusive  are  very  similar  to 
those  for  the  same  uses  in  the  boiler  shop.  Particular  shaped  blades 
are  used  on  shears  for  shearing  structural  shapes. 

Much  of  the  work  of  shaping  ship  material  is  done  cold,  except 
that  of  bending  angles  and  other  structural  shapes  on  the  bending 


Closely  associated  with  the  equipment  of  this  shop  are  such  tools 
as  the  portable  hydraulic  riveter,  pneumatic  riveters,  chippers,  drills 
and  countersinks,  used  in  the  work  of  riveting  together  the  frames 
and  plates  of  the  ship's  hull. 

409.  The  Bending  Slab.— Fig.  258  shows  a  level  floor  of  heavy 
cast-iron  slabs  used  for  bending  angles  and  other  structural  shapes  to 
various  curved  forms  for  ship  frames.  The  slabs  are  well  sup- 
ported on  permanent  foundations,  and  the  regularly  spaced  square 
holes  in  them  are  used  to  hold  various  pins  and  eccentric  washers 
against  which  the  frame  is  bent. 

To  arrange  for  bending,  a  wooden  template  giving  the  required 
curve  of  the  frame  is  placed  on  the  slabs  and  the  curve  is  marked 
thereon  with  chalk.  Pegs  and  washers  are  placed  in  the  square 
holes  along  the  chalk  mark  as  guides  against  which  the  frame  is 


OTHER  SHOPS — SPECIAL  PROCESSES  375 

to  be  bent.  An  angle  bar  or  otber  long  piece  to  be  bent  is  heated 
to  a  red  heat  in  the  long  furnace  shown  in  the  background.  The 
view  shows  the  workmen  in  the  act  of  dragging  an  angle  from  the 
furnace.  This  is  dragged  out,,  one  end  is  secured  between  two  pegs 
at  one  end  of  the  curve  outlined  on  the  slabs,  and  the  other  end  is 
dragged  by  suitable  bars  and  other  appliances  against  the  guide 
pins  and  there  clamped  until  cold.  Very  convenient  clamps  or  dogs 
for  this  use  consist  of  heavy  round  bars  of  iron  bent  into  a  flattened 


FIG.  258. — Bending  Slab  and  Heating  Furnace. 

V-shape,  i.  e.,  with  the  two  legs  slightly  less  than  90°  to  each  other. 
One  leg  is  set  in  a  slab  hole  and  as  the  other  comes  against  the 
work,  a  stroke  of  the  hammer  sets  it  tightly  in  a  leaning  position 
in  the  hole. 

410.  Special  Processes. — A  few  special  processes  are  outlined  in  the 
paragraphs  which  follow.     These  are  selected  because  of  the  im- 
portance of  their  products   or  because  of  the  application  of  the 
processes  themselves  to  many  different  needs. 

411.  Malleableizing. — This  is  the  process  of  rendering  cast-iron 
castings  malleable,  or  capable  of  bending  without  breaking.  Castings 


376  MECHANICAL  PROCESSES 

are  not  only  relieved  of  brittleness,  but  a  considerable  degree  of  tough- 
ness and  ductility  is  imparted  to  them.  Many  small  articles  of  iron 
in  every-day  use,  notably  iron-pipe  fittings,  are  far  more  readily 
inade  as  castings  and  malleableized  afterward,  than  if  made  of 
wrought  iron  or  mild  steel  at  the  beginning.  This  process  practically 
converts  them  into  a  mild  steel  by  the  removal  of  carbon,  and  its 
method  of  application  is  as  follows : 

Iron  boxes  of  convenient  size,  known  as  annealing  pots,  are 
filled  with  castings,  each  of  which  is  entirely  surrounded  by  some 
kind  of  iron  oxide,  usually  mill  scale,  squeezer  scale,  or  pure  mag- 
netic ore.  The  castings  have  been  thoroughly  cleaned  of  sand  and 
fins  or  other  projections  of  metal  before  leaving  the  foundry,  and 
a  good  sprinkling  with  sal  ammoniac  will  give  them  a  coating  of 
rust,  which  as  iron  oxide,  assists  in  malleableizing. 

Each  pot  is  closed  with  a  thin  iron  cover  luted  with  clay  and 
may  be  placed  in  any  kind  of  a  furnace  in  which  a  steady  heat  may 
be  maintained.  In  malleableizing  works,  several  hundred  post  are 
stacked  in  a  large  furnace  heated  with  producer  gas.  The  brick- 
lined  iron  door  of  this  furnace  is  closed,  the  contents  are  heated  up 
to  about  1800°  in  24  hours,  are  maintained  at  this  heat  about  48 
hours,  and  then  allowed  to  cool  gradually.  At  the  high  heat  main- 
tained, the  castings  give  up  their  uncombined  carbon  to  the  oxygen 
of  the  iron  oxide,  and  when  removed  they  have  lost  the  brittleness 
of  cast  iron. 

This  process  is  not  so  much  in  general  use  as  formerly.  Many 
castings  are  now  displaced  by  drop  forgings  and  articles  of  pressed 
sheet  steel.  These  are  neater  looking  and  of  less  bulk  than  the 
usual  run  of  malleable  castings.  Some  shapes  are  cheapest  made 
as  castings,  however. 

412.  Case  Hardening. — This  process  is  the  reverse  of  malleableiz- 
ing, i.  e.j  it  adds  carbon  to  forgings  of  wrought  iron  or  mild  steel  to 
make  them  hard  for  resisting  wear.  Many  articles,  .such  as  set 
screws,  bolts  and  nuts,  jaws  of  wrenches,  etc.,  subject  to  unusual 
wear,  are  much  increased  in  durability  by  case  hardening  after 
they  are  machined  to  shape.  The  process  is  as  follows . 

A  number  of  forgings,  each  of  which  is  surrounded  by  carbon 
substances  such  as  ground  bone  and  charred  leather,  are  packed 
in  an  iron  box.  The  box  lid  is  luted  with  clay  and  the  box  is  heated 


OTHER  SHOPS — SPECIAL  PROCESSES 


377 


gradually  in  a  suitable  furnace  up  to  a  temperature  ranging  from 
1400°  to  1700°  F.  This  heat  is  maintained  from  6  to  14  hours. 
The  degree  of  heat  applied  depends  upon  the  grade  of  steel  in  the 
forgings,  and  the  duration  of  the  heating  depends  upon  the  depth 
of  the  hardness  required.  The  object  of  the  process  is  to  increase 
the  amount  of  combined  carbon  in  the  forgings,  as  in  the  cementa- 
tion process  of  steel  making.  The  articles  are  removed  from  their 
boxes  when  cool  enough  to  handle  and  are  heated  up  to  critical 
temperature  and  hardened  by  quenching  in  water  or  oil. 

This  process  of  hardening  sometimes  warps  forgings  slightly,  a 
fault  which  may  be  in  some  cases  very  objectionable. 


FIG.  259.— Form  for  Bending  Small  Pipes  by  Hand. 

413.  Pipe  Bending. — Mention  has  been  made  in  another  paragraph 
of  methods  of  bending  copper  pipes  and  small  iron  or  brass  pipes. 

Two  essentials  in  pipe  bending  are  (1)  to  keep  the  pipe  from 
flattening  into  elliptical  shape  in  the  bend,  and  (2)  to  avoid 
wrinkles  in  the  concave  part  of  the  bend.  These  may  be  accom- 
plished by  bending  the  pipe  over  a  grooved  form  shown  in  Fig. 
259.  The  sides  of  the  form  may  be  extended  well  above  the  groove 
to  hold  the  sides  of  the  pipe  against  bulging  along  the  bend.  This 
form  may  be  used  for  cold  bending  of  pipes  up  to  about  IJ-inch 
diameter. 


378 


MECHANICAL  PROCESSES 


A  more  elaborate  form,  suited  to  larger  piping,  is  shown  in 
Fig.  260.  Large  pipes  should  be  heated  red  to  facilitate  bending. 

A  pipe  may  be  filled  with  sand  and  plugged  to  assist  in  holding 
its  circular  cross  section,  and,  if  a  bending  form  is  not  available, 
the  jaws  of  a  vise  may  be  spread  apart  just  far  enough  for  the  pipe 
to  be  held  between  them  during  bending.  This  will  keep  the  pipe 
sides  from  bulging.  The  welded  seam  of  a  pipe  should  be  in  the 
throat  or  concave  part  of  the  bend. 


FIG.  260. — Form  for  Bending  Large  Pipes. 

414.  Joining  Metals. — There  are  now  in  use  many  important 
means  of  uniting  metals  solidly  together.  These  have  many  applica- 
tions in  manufacturing  and  one  or  more  of  them  may  frequently  be 
availed  of  in  making  permanent  repairs,  to  broken  machinery  or 
equipment  under  emergency  conditions. 

Methods  of  joining  metals  include  the  following,  some  of  which 
have  been  described : 

(1)  Soldering.  (6) 

(2)  Brazing. 

(3)  Welding  at  the  forge.         (7) 

(4)  Electric  welding.  (8) 

(5)  Thermit  welding. 

Closely  akin  to  these  methods  is  the  use.  of  metal  cements,  which 
stop  cracks  in  castings,  seams,  and  joints  of  patches  held  in  place 
by  aid  of  bolts  and  iron  straps.  A  leaky  pipe  or  boiler  seam  may 
often  be  stopped  by  the  use  of  sal  ammoniac  and  iron  filings,  or  by 
a  mixture  of  Portland  cement  and  coal  tar.  A  patented  compound 


Oxy-acetylene   and    oxy-hy- 

drogen   welding. 
Burning  on. 
Puddling. 


OTHER  SHOPS — SPECIAL  PROCESSES  379 

known  as  Smooth  On  is  very  effective  for  mending  broken  ma- 
chinery parts  and  repairing  leaks  in  boilers,  tanks  and  castings. 

Joining  metals  implies  an  actual  metal  to  metal  contact.  There 
is  always  an  oxide  or  other  coating  over  a  metal  surface  exposed  to 
air.  This  must  be  removed  before  two  metals  can  be  joined,  and 
it  is  done  principally  by  scraping,  filing,,  pickling,  etc.  The  last 
thin  coating  of  oxide  which  forms  during  heating  is  removed  by 
action  of  a  flux.  Union  between  the  two  metals  is  then  accom- 
plished (1)  by  bringing  the  contact  surfaces  of  both  metals  up  to 
the  melting  point  of  at  least  one  of  them,  as  in  soldering  and  braz- 
ing, which  necessitates  the  melting  of  the  solder  or  brazing  metal, 
or  (2)  by  bringing  both  metals  to  a  state  of  incipient  fusion  at  the 
points  where  they  are  to  be  welded  and  pressing  them  together 
firmly. 

There  seems  no  doubt  that  the  process  of  welding  iron  or  steel 
detracts  from  their  strength.  The  weld  may  not  break  under  a 
tensile  test,  but  the  metal  on  one  side  of  the  weld  may  break  instead. 
The  high  heating  necessary  for  welding  changes  the  grain  size  of 
iron  and  steel,  making  it  coarse  and  thus  weaker  than  before.  This 
condition  can  be  remedied  by  reheating  welded  bars  to  the  critical 
point  and  in  this  way  restoring  the  fine  grain  size,  or  in  a  measure 
by  a  thorough  hammering  while  the  weld  is  yet  very  hot. 

415.  Electric  Welding. — When  an  electric  current  encounters  re- 
sistance in  its  circuit  a  portion  of  its  energy  is  converted  into  heat. 
If  an  electric  current  flows  across  the  junction  of  two  rods  placed 
in  mutual  contact,  more  or  less  heat  will  be  generated  at  this  joint. 
If  the  joint  does  not  present  great  resistance,  a  weak  current  will 
traverse  it,  and  a  large  quantity  of  current  will  be  required  to 
generate  enough  heat  to  weld  the  rods  together.  If,  however,  the 
joint  presents  moderate  resistance,  due  to  the  rod  ends  being  more 
or  less  separated  by  air  space,  or  by  scale,  sand,  or  other  non-con- 
ductor, a  stronger  current  is  required  to  flow  across  the  resistance, 
and  a  much  less  quantity  of  current  will  produce  a  welding  heat. 

Application  is  made  of  these  conditions  in  electric  welding  opera- 
tions. The  first-named  condition,  that  requiring  the  lesser  strength 
of  current  is  known  as  the  resistance  system,  and  the  second  con- 


380  MECHANICAL  PROCESSES 

dition,  requiring  strong  enough  current  to  produce  an  electric  arc, 
is  called  the  arc  system.  In  both  systems  the  strength  and  quantity 
of  current  for  welding  depends  upon  the  size  of  the  weld  and  the 
time  consumed  in  making  it.  The  ordinary  lighting  circuit  is 
strong  enough  for  many  needs  in  welding. 

416.  The  Resistance  System. — This  system,  developed  by  Prof. 
Elihu  Thompson,  is  much  used  to  weld  together  wires,  rods,  small 
forgings  and  other  parts  which  are  made  separately  for  quick  produc- 
tion. It  is  used  in  welding  links  of  chains,  rings,  wire  fence*  meshes, 
wheel  tires,  valves  and  their  stems.,  lengths  of  steel  steam  pipe  and 
their  flanges,  branch  outlets,  steam  drums,  etc.  Different  kinds 
of  metal  may  be  welded  in  one  piece  provided  their  melting  points 
do  not  differ  much. 


FIG.  261. — Electric  Welding  Clamps. 

The  essential  features  of  the  welding  apparatus  of  this  system 
are  shown  in  Fig.  261.  The  pieces  R  and  8  to  be  joined  are  held 
firmly  together  in  the  desired  relative  position  by  heavy  copper 
clamps  C  and  D,  one  of  which  may  be  moved  toward  the  other. 
Current  travels  along  the  circuit  through  Cf  R,  8  and  D, 
and  when  the  two  ends  R  and  S  are  softened  by  heat,  they  are 
mashed  together  by  the  pressure  of  the  clamps,  forming  an  ex- 
panded burr  which  is  later  cut  off.  In  some  machines,  however, 
a  swage  surrounds  the  joint  at  the  time  of  welding,  avoiding  the 
burr  and  pressing  the  metal  together  very  firmly  in  a  lateral 
direction. 

Alternating  current  is  required  in  this  system  of  welding.  It 
heats  both  sides  of  the  joint  more  evenly. 

417.  The  Arc  System. — This  system  is  used  in  repairing  iron  cast- 
ings in  a  way  which  resembles  soldering.  A  crack  or  cavity  is  filled  up 


OTHER  SHOPS — SPECIAL  PROCESSES 


381 


with  drops  of  cast  iron  or  cast  steel  which  melt  from  a  rod  as 
shown  in  Fig.  262.  This  view  shows  the  method  of  filling  a  blow- 
hole cavity  in  the  end  of  the  cast-iron  mill-roll  R.  The  upper  end 
of  the  roll  (shown  in  cross  section)  is  surrounded  by  a  piece  of 
pressed  coke  &  enclosed  in  moulding  sand  c  held  in  a  sheet-iron 
casing  d.  Enclosing  the  whole  upper  end  of  the  roll  is  a  mass  of 
coke  ~k  surrounded  by  a  checker-work  g  of  fire  bricks.  This  body  of 
coke  smoulders,  keeping  the  roll  hot  during  welding.  A  rod  of 
cast  iron  s  is  clamped  to  the  positive  lead  p  of  a  direct-current  con- 
ductor, and  is  manipulated  by  the  insulated  handle  h.  The  nega- 
tive lead  n  of  the  circuit  is  attached  to  the  roll  at  a  convenient  point. 


FIG.  .262.— Arrangement  for  Arc  Welding. 

The  lower  end  of  the  rod  s  is  melted  away  by  the  arc,  and  is  de- 
posited in  the  cavity  until  the  latter  is  filled. 

418.  The  Thermit  Process. — The  essential  feature  of  this  process 
consists  of  generating,  by  chemical  union  between  oxygen  and  alumi- 
num, an  intense  local  heat  which  produces  from  the  reaction  a 
certain  amount  of  molten  iron.  This  iron,  which  is  in  the  nature 
of  mild  steel,  may  be  run  into  a  mould  to  form  a  small  casting,  or 
may  be  run  between  the  two  parts  of  a  broken  forging  or  steel 
casting  to  form  a  weld.  The  welding  of  cast  iron  by  this  process 
is  very  difficult  because  the  heat  of  the  process  burns  out  the  un- 
combined  carbon  of  the  casting,  making  it  hard,  brittle,  and  of  un- 
certain strength. 

Aluminum  and  oxygen  have  a  very  strong  chemical  affinity  for 
each  other.  A  mixture  of  finely  ground  aluminum  and  iron  oxide 
25 


382  MECHANICAL  PROCESSES 

in  proper  chemical  proportion,  known  by  the  trade  name  Thermit, 
will,  when  ignited,  burn  with  an  intense  heat  and  release  molten 
iron  which  may  be  used  as  stated.  The  chemical  reaction  is  ex- 
pressed by  Fe203  +  2Al  =  Al203  +  2Fe.  More  iron  than  comes  from 
the  oxide  may  be  supplied  by  placing  iron  punchings  in  the  mixture 
before  it  is  ignited,  and  the  heat  of  the  reaction  will  melt  this  iron 
and  mix  it  with  that  formed  from  the  iron  oxide. 

Ignition  'is  accomplished  by  an  ignition  powder  consisting  of 
barium  oxide  mixed  with  powdered  aluminum.  A  small  quantity 
of  this  placed  on  top  of  a  thermit  charge  and  ignited  with  a  match, 
will  start  the  burning  of  the  thermit. 

This  process  is  advantageously  used  in  welding  broken  locomotive 
frames,  spokes  of  heavy  cast-steel  wheels,  ships'  stern  posts,  rudder 
posts,  propeller  struts  and  breaks  in  other  large  forgings  or  steel 
castings,  without  removing  them  from  their  places.  Its  heat  is  also 
used  in  welding  together  lengths  of  heavy  wrought  iron  or  steel 
pipe.  Lengths  of  street  railway  rails  which  are  prevented  by  street 
paving  from  subsequent  bending  under  expansion  due  to  the  sun's 
heat  are  smoothly  and  economically  welded  by  this  method.  It  is 
particularly  suited  to  large  work  and  is  not  economical  for  small 
work. 

419.  Making  a  Thermit  Weld. — The  simplicity  of  the  equipment 
for  thermit  welding  or  casting  makes  it  particularly  valuable  for  work 
far  removed  from  shop  facilities.  A  quantity  of  thermit  is  placed 
in  a  conical,  covered  crucible  as  shown  at  A  in  Fig.  263.  This 
micible  is  made  of  sheet  iron,  magnesite  lined,  and  the  opening  in 
the  lower  end  is  stopped  by  a  pin  resembling  a  long  nail  over  which 
is  placed  a  small  disc  of  asbestos,  a  disc  of  iron  and  a  little  loose, 
refractory  sand. 

The  ragged  ends  of  the  two  broken  parts  to  be  welded  are  drilled 
or  otherwise  cut  so  that  when  in  correct  position  there  is  a  space 
of  about  -J  inch  between  them.  They  are  then  clamped  rigidly  and 
the  break  is  surrounded  by  a  close-fitting  mould  made  up  of  fire 
bricks  and  baked  sand  shapes  of  the  required  forms  to  afford  open- 
ings as  shown  at  B  (Fig.  263)  and  to  allow  a  collar  of  metal  to  be 
formed  partially  around  the  break  in  addition  to  the  metal  which 
fills  it.  All  cracks  in  the  mould  must  be  carefully  luted  with  fire 
clay  to  prevent  the  loss  of  metal  through  them. 


OTHER  SHOPS — SPECIAL  PROCESSES 


383 


The  crucible  is  now  suspended  so  that  the  opening  is  a  few  inches 
above  the  pouring  gate.  This  completes  the  preparations. 

The  first  step  toward  the  actual  welding  operation  consists  of 
heating  the  ends  of  the  broken  parts  to  a  red  heat  by  directing 
the  flame  of  a  gasolene  compressed-air  torch  through  the  heat- 
ing gate  of  the  mould.  When  this  is  done,  quickly  stop  this 
gate  with  a  dry  sand  core  made  for  that  use,  and  apply  a  match 
or  burning  splinter  to  the  ignition  powder  on  top  of  the  crucible 
charge.  The  reaction  which  follows  evolves  heat  and  smoke 
but  is  not  explosive.  It  ceases  after  a  moment,  leaving  the  crucible 
full  of  very  hot  molten  mild  steel  which  is  tapped  into  the  mould 
by  a  sharp  upward  knock  on  tlie  pin  end  in  the  bottom  of  the 


/f/se/r 


Oaf* 


Gate 


FIG.  263. — Moulds  Crucible.    Thermit  Welding. 

crucible.  A  small  quantity  of  slag  (A1203)  formed  by  the  reaction 
floats  on  the  metal. 

A  mould  may  be  made  about  a  break  by  filling  the  break  and  the 
space  for  the  metal  collar  with  wax,  around  which  is  built  an  ordi- 
nary sand  mould  provided  with  the  same  openings  shown  in  B,  Fig. 
263.  This  mould  is  contained  in  a  sheet-iron  box  and  the  sand 
must  be  thoroughly  dried.  The  wax  is  melted  out  when  the  torch 
is  applied  for  heating  before  running  the  steel  into  the  mould. 

Thermit  steel  must  run  into  a  mould  under  the  break  and  rise 
until  the  first  metal,  which  chills  in  heating  the  mould,  flows  out 
over  the  top  of  the  riser  hole.  This  insures  the  thorough  softening 
and  joining  of  the  broken  parts  with  the  molten  steel  which  unites 
them. 


384  MECHANICAL  PROCESSES 

After  the  weld  has  cooled,,  the  mould  is  removed,  the  joint  is 
smoothed  up,  and  it  is  then  annealed  by  maintaining  a  coke  or 
charcoal  fire  all  around  it  for  5  or  6  hours  and  allowing  it  to  cool 
slowly. 

420.  Blow  Pipe  Welding. — The  flame  of  a  combustible  gas  may  be 
so  regulated  in  its  shape  and  intensity  by  a  properly  constructed 
burner  that  it  can  be  effectively  used  for  local  heating  such  as  is 
needed  in  welding.  In  the  compound  blow  pipe,  a  type  of  which  is 
shown  in  Fig.  264,  oxygen  is  admitted  to  one  tube  of  the  burner  and 
a  combustible  gas  is  admitted  to  the  other  tube.  These  two  gases  pass 
along  the  channels  1  and  2,  mix  in  the  small  receptacle  3,  and  finally 
pass  from  the  nozzle  at  4  where  they  enter  the  flame. 

Oxygen  is  supplied  from  a  steel  cylinder  in  which  it  is  stored 
under  a  pressure  of  100  atmospheres  or  more,  passing  through  a 


FIG.  264. — Compound  Blow  Pipe. 

reducing  valve  which  lowers  the  pressure  to  30  pounds  or  less  per 
square  inch  in  the  burner. 

Hydrogen  and  acetylene  gas  are  much  used  as  the  combustible  gas. 
They  may  also  be  stored  in  steel  cylinders  as  a  convenient  means  of 
transporting  them  from  the  factories  which  make  them,  but  acety- 
lene gas  is  so  easily  produced  that  it  is  frequently  made  where  it  is 
used.  Great  care  must  be  taken  to  avoid  an  explosion  in  using  or 
handling  any  kind  of  inflammable  gas.  Acetylene  is  stored  in  steel 
cylinders  with  acetone,  a  liquid  which  absorbs  a  large  volume  of  the 
gas  under  heavy  pressure,  thus  avoiding  the  danger  of  this  par- 
ticular gas  when  compressed.  In  its  simple  process  of  production — 
that  of  admitting  water  to  calcium  carbide  in  a  closed  vessel — its 
explosive  tendency  is  not  always  realized.  A  spark  of  flame  coming 
in  contact  with  the  gas  will  cause  an  explosion  in  force  and  volume 
depending  upon  the  amount  of  gas  and  oxygen  or  air  in  mutual 
contact. 


OTHER  SHOPS — SPECIAL  PROCESSES  385 

As  the  mixture  of  oxygen  and  gas  flows  from  the  blow  pipe,  it 
burns  in  a  flame  which  is  regulated  to  suit  the  work  to  be  done. 
The  supply  of  each  gas  is  so  controlled  by  a  small  valve  that  the 
relative  amounts  and  pressures  of  the  two  may  be  regulated  as 
needed.  The  gas  mixture  should  issue  from  the  blow-pipe  nozzle 
rapidly  enough  to  keep  the  flame  from  following  the  mixture  back 
into  the  pipe,  and  on  the  other  hand  the  flame  should  not  receive 
too  strong  a  blast  by  too  rapid  a  flow  of  gas.  The  quantity  of 
oxygen  must  be  kept  down  enough  to  avoid  an  oxidizing  flame  in 
welding. 

Slightly  different  forms  of  blow  pipes,  determined  by  experiment, 
are  necessary  for  burning  gases  under  different  pressures  and  differ- 
ent intensities  of  flame,  according  to  the  requirements  outlined  in 
the  preceding  statements, 

.        f 


FIG.  265. — Methods  of  Welding  Plate  Edges. 

421.  Method  of  Making  a  Blow  Pipe  Weld.— The  ease  with  which 
an  oxy-acetylene  or  an  oxy-hydrogen  outfit  may  be  set  up  where 
needed,  and  the  small  size  of  the  blow  pipe  and  its  flexible  rubber- 
hose  connections,  make  such  an  outfit  very  practical  and  convenient 
for  use  on  work  which  demands  local  heating. 

In  making  a  weld,  two  sheets  of  metal  are  butted  edge  to  edge 
in  a  clean,  close-fitting  joint  as  shown  at  A,  Fig.  265.  Two  blow- 
pipe flames  are  held  at  a  and  &  on  opposite  sides  of  the  plates, 
directly  opposite  each  other,  and  a  short  length  along  the  seam  is 
heated  to  welding  heat.  With  one  of  the  pieces  properly  supported 
to  hold  it  firmly  in  place,  the  other  may  be  struck  with  a  hammer  to 
bring  about  the  weld  through  the  closer  contact  due  to  the  blow. 

Another  method  of  welding  is  shown  at  5,  Fig.  265.  A  sheet  of 
metal  rolled  to  cylindrical  form  presents  its  edges  in  V-shape  as 
at  c.  These  edges  are  temporarily  held  together  by  bolts  and  straps. 


386  MECHANICAL  PROCESSES 

A  blow-pipe  flame  is  directed  into  the  joint  to  bring  it  to  welding 
heat,  and  at  the  same  time  a  heavy  wire  of  pure  Xorway  iron  is 
held  so  that  the  flame  melts  its  end.  The  drops  of  fused  metal 
from  the  wire  run  into  and  fill  the  joint,  resembling  the  process  of 
soldering,  until  the  entire  notch  is  filled  with  solid  metal.  The  joint 
should  be  hammered  while  hot  to  restore  the  grain  size  of  the  fused 
metal  and  increase  its  strength.  The  joint  needs  no  particular 
cleaning  nor  any  flux  before  welding  is  begun. 

A  thicker  sheet  of  metal  may  be  cut  at  the  edges  to  form  a  joint 
as  at  d,  and  is  welded  along  the  upper  notch  and  then  rolled  half- 
way around  and  welded  along  the  lower  notch. 

A  poor  joint  will  result  if  the  operator  allows  drops  of  metal  to 
fall  upon  a  part  of  the  seam  not  heated  to  welding  temperature. 

422.  Application  of  Blow-Pipe  Welding. — This  method  is  much 
used  to  join  the  edges  of  wrought  iron  or  steel  plates  up  to  an  inch  or 
more  in  thickness.  Heavy  plates  conduct  away  the  heat  so  rapidly 
that  it  may  not  be  possible  for  the  burner  to  raise  the  seam  to  welding 
temperature.  Steel  castings  may  also  be  wielded,  and  cracks  or  blow 
holes  may  be  filled  with  drops  of  molten  iron.  Brass  castings  may 
be  repaired  by  melting  into  a  crack,  cavity  or  blow  hole,  drops  of 
brass  from  a  rod  of  the  same  composition  as  the  casting. 

The  difficulty  of  welding  iron  is  in  proportion  to  the  amount  of 
carbon  it  contains,  and,  while  some  operators  claim  ability  to  weld 
or  mend  cast  iron,  it  is  difficult  to  do  so.  A  cast-iron  bar  may  be 
fused  at  the  end  into  drops  which  will  weld  to  a  properly  heated 
cast-iron  surface,  but  the  iron  will  not  be  homogeneous  and  it  may 
be  too  brittle  for  strength  and  too  hard  for  machining. 

Aluminum  may  be  welded,  under  blow-pipe  heat,  by  use  of  a  flux 
which  removes  the  oxide,  although  this  metal  cannot  be  soldered  or 
brazed,  at  least  by  usual  means. 

Steel  pipes  and  flanges  may  be  welded  together,  and  lengths  or 
branches  welded  in  one  piece. 

A  particular  application  of  gas  welding  is  that  used  in  welding 
the  longitudinal  seam  of  a  boiler  drum  made  of  one  sheet  of  metal. 
The  drum  is  mounted  on  a  machine  especially  built  to  handle  it 
readily  and  quickly.  The  machine  carries  two  specially  constructed 


OTHER  SHOPS — SPECIAL  PROCESSES  387 

burners  which  travel  along  on  opposite  sides  of  the  lapped  plate 
edges,  heating  them  to  welding  heat.  The  burners  are  followed  by 
rollers  which  exert  great  enough  pressure  to  make  the  weld  and  to 
press  the  seam 'down  to  the  thickness  of  the  plate.  Water  gas  and 
air  are  used  in  the  burners.  The  strength  of  such  a  welded  joint  is 
about  90  or  95%  that  of  the  solid  plate,  although  the  ordinary  oxy- 
acetylene-welded  joint  is  not  over  about  80  or  85%  of  the  plate 
strength. 

423.  Blow-Pipe  Cutting  of  Metals. — A  remarkable  method  of  cut- 
ting metals  has  been  developed  in  the  use  of  the  oxy-hydrogen  and 
oxy-acetylene  burners. 

To  a  blow  pipe  used  for  heating  is  attached  an  additional  tube 
through  which  a  jet  of  oxygen  is  blown  from  a  supply  tank.  The 
blow-pipe  flame  heats  the  metal  to  be  cut,  and  when  so  heated,  the 
small  jet  of  oxygen  directed  against  it  burns  a  narrow  cut  along  any 
path  over  which  the  flame  may  be  directed.  So  readily  do  oxygen 
and  red-hot  metals  unite,  that  such  a  burner  is  used  to  cut  plates  of 
metals,  including  steel  armor,  up  to  9  inches  thick.  The  width  of 
the  cut  is  not  over  J  inch  and  the  metal  on  each  side  of  the  cut  is 
unchanged  in  grain  size  or  otherwise.  Tubes,  shafts,  and  structural 
shapes  may  be  easily  and  quickly  cut  by  this  means,  although  there 
is  difficulty  in  cutting  cast  iron  due  apparently  to  the  carbon  it 
contains.  Eivet  heads  are  quickly  cut  off  without  marring  the 
riveted  plates,  and  any  tangled  mass  of  iron  or  steel  wreckage,  old 
boilers,  or  the  hull  of  a  ship  may  be  easily  cut  to  pieces  by  this 
method.  In  cutting  a  hole  of  several  inches  diameter  in  a  steel 
plate,  a  small  hole  is  first  drilled  to  give  the  burner  a  start, 

Hydrogen  is  more  effective  for  this  cutting  than  is  acetylene,  as 
the  former  makes  a  hotter  flame.  For  light  cutting,  a  blow  pipe 
may  be  used  which  has  no  extra  oxygen  tube  attached.  The 
flame  is  given  an  excess  of  oxygen  from  the  regular  tube,  making  it 
an  oxidizing  flame. 

424.  Burning  On. — This  is  a  method  employed  for  mending  a 
cracked,  broken,  or  honey-combed  casting  of  cast-iron  or  brass.  Many 
costly  castings  which  would  otherwise  have  to  be  discarded  may  be 
made  sound  by  this  process,  although  defects  in  some  cases  are  too  ex- 
tensive, or  are  not  well  located  for  practical  repairing. 


388 


MECHANICAL  PROCESSES 


The  application  of  the  method  is  illustrated  in  Fig.  266.  The 
view  A  shows  the  casting  to  be  repaired  and  B  shows  the  same  cast- 
ing bedded  in  sand  and  otherwise  prepared  for  the  work.  Let  it 
be  supposed  that  the  portion  b  of  the  upper  flange  of  A  is  cracked 
or  filled  with  blow  holes.  The  defect  is  chipped  out  to  present  a 
slit  or  cavity  which  shows  sound  metal.  Supporting  the  casting 
firmly  on  the  foundry  floor,  surround  the  defective  part  with  a 
mould  made  of  baked  sand  cores  and  fire  bricks  wedged  and  clamped 
in  place.  The  joints  between  bricks  and  cores  are  carefully  plastered 
with  clay.  It  is  essential  to  leave  either  a  small  hole  c  leading  from 
the  bottom  of  the  mould.,  or  one  at  d  leading  from  the  highest  point 
at  which  the  metal  is  to  stand  in  the  mould.  Both  openings  may  be 


A 


FIG.  266. — Mending  a  Casting. 

provided  if  desired,  and  each  leads  into  a  sand  basin  which  holds 
metal  as  it  flows  from  the  mould.  After  assembling  and  securing 
the  mould  around  the  defect,  the  casting  must  be  heated  by  means 
of  a  gasolene  torch  or  blow  pipe.  This  heating  may  be  slowly  done 
by  using  a  charcoal  fire,  and  sometimes  the  position  of  the  defect 
is  such  that  heating  must  be  done  before  the  mould  parts  are  placed. 
When  the  casting  is  nearly  or  quite  red  hot,  a  ladle  of  molten  metal 
of  the  same  composition  as  the  casting  is  held  over  the  opening  g 
in  the  upper  core,  and  a  steady  stream  is  poured  into  the  mould, 
keeping  it  filled.  The  first  metal  poured  in  serves  merely  to  heat 
and  soften  the  metal  around  the  defect,  and  is  allowed  to  flow  out. 
The  stream  of  molten  metal  is  continued  until  it  has  about  melted 
the  metal  adjacent  to  the  defect.  A  small  iron  rod  is  used  to  deter- 


OTHER  SHOPS — SPECIAL  PROCESSES 


389 


mine  this  condition.  The  lower  open  c  is  then  stopped  with  a  shovel 
full  of  dry  earth,  and  the  mould  is  left  full  of  metal.  The  casting  is 
covered  with  a  few  pieces  of  sheet  iron  and  allowed  to  cool  slowly. 
When  cool,  the  defect  will  be  found  filled  with  solid  metal  which  can 
be  trimmed  to  the  contour  of  the  casting. 

Cast  iron  may  be  brazed  by  means  of  spelter  as  described  for 
brazing  copper.  It  is  essential  (1)  that  the  broken  parts  be 
thoroughly  free  of  scale,  dirt  and  grease;  (2)  that  they  be  clamped 
in  their  correct  relative  position;  (3)  that  heating  be  done  evenly 
in  a  clean  fire,  and  (4)  that  the  spelter  be  applied  along  every  part 
of  the  break. 

425.  Puddling. — This  is  a  method  of  repairing  small  broken  cast- 
ings similar  to  burning  on.  A  mould  of  clay  or  plaster  of  Paris  is 
formed  about  the  broken  parts  of  a  small  casting  as  shown  at  6, 


f$$$|^ 


FIG.  267. — Uniting  a  Broken  Casting. 

Fig.  267.  When  dry,  the  mould  holds  the  casting  firmly.  Both 
are  supported  in  a  box  of  sand,  and  the  fracture  is  heated  with  an 
oxy-hydrogen  or  an  oxy-acetylene  blow  pipe.  At  the  same  time  a 
rod  of  metal  is  held  in  the  flame  so  that  the  end  melts  and  joins 
the  highly  heated  ends  of  the  casting.  These  ends  are  kept  prac- 
tically molten  until  enough  metal  has  melted  from  the  rod  to  join 
them  together. 

After  the  casting  has  cooled,  the  superfluous  metal  is  ground 
away.  This  method  of  mending  castings  burns  out  the  carbon  of 
cast  iron  and  makes  the  joint  harder  and  more  brittle  than  the  iron 
of  the  casting. 

426.  Classification  of  Welding  Methods, — Those  methods  which 
accomplish  the  union  of  two  pieces  of  metal  directly  by  fusion  of  one 
to  the  other,  without  the  intervention  of  another  metal  at  the 
joint,  are  classed  as  autogenous  methods.  Those  which  accomplish 
union  between  two  metals  by  means  of  an  intermediate  metal,  as  in 
soldering  and  brazing,  are  classed  as  heterogeneous  methods. 


390  MECHANICAL  PROCESSES 

427.  Grinding". — The  popular  idea  of  grinding  is  its  use  in  shaping 
more  or  less  roughly  the  edges  of  cutting  tools  and  in  removing 
fins  and  other  small  projections  from  forgings  and  castings  as  a 
step  toward  making  them  smooth. 

Developments  in  recent  years  in  the  production  of  grinding 
wheels  of  many  shapes  and  degrees  of  hardness  and  the  fitting  of 
these  wheels  to  high-grade  machines  for  controlling  their  motions, 
have  brought  into  practical  use  methods  of  grinding  which  pro- 
duce smooth  and  true  surfaces  of  a  degree  of  accuracy  not  attainable 
by  any  other  known  means. 

Work  is  now  roughed  out  on  the  lathe,  planer,  milling  machine 
and  other  machine  tools  and  is  finished  to  any  desired  degree  of 
accuracy  better,  cheaper  and  quicker  by  grinding  machines  than 
by  other  means.  This  applies  to  the  ordinary  as  well  as  to  the 
finest  finishing,  and  it  applies  also  to  metals  of  all  degrees  of 
hardness. 

428.  Grinding  Machines. — Machines  for  accurate  grinding  are 
usually  built  on  the  general  lines  of  either  a  lathe  or  a  milling 
machine.     In  these  machines,  the  grinding  wheel  takes  the  place  of 
the  cutting  tool,  and  it  is  so  mounted  that  it  can  be  revolved  at  high 
speeds  suited  to  the  work. 

The  grinding  lathe  holds  work  between  centers,  or  in  special 
chucks,  and  the  wheel  may  be  fed  along  the  lathe  bed  as  it  revolves 
in  light  contact  with  the  cylindrical  work  to  be  ground.  This 
machine  is  used  for  grinding  engine  valve  stems,  piston  rods,  and 
any  similar  cylindrical  work.  Crank  shafts  of  automobile  or  other 
small  engines  are  finished  from  the  rough  forging  in  this  machine. 

The  milling  machine  form  of  grinder  may  be  either  a  plain  or 
a  universal  machine.  Work  may  be  placed  on  its  movable  table  for 
flat  grinding,  or  the  usual  lathe  center  attachments  may  be  used 
to  support  work  for  internal  and  external  cylindrical  or  other 
curved-surface  grinding.  In  these  machines,  the  rapidly  revolving 
grinding  wheel  takes  place  of  the  milling  cutter.  These  machines 
are  used  for  grinding  drills,  milling  cutters,  cams,  parts  of  many 
articles  made  in  quantity  such  as  guns,  pistols,  tools,  and  an  end- 
less variety  of  small  castings  and  forgings  requiring  machine 
finishing. 

The  spindle  which  carries  a  grinding  wheel  and  the  bearings  in 


OTHER  SHOPS — SPECIAL  PROCESSES  391 

which  it  rests  are  made  with  the  greatest  accuracy  possible  and  are 
fitted  to  allow  no  play  whatever  between  spindle  and  bearing. 
Grinding  may  be  either  wet  or  dry,  but  wet  grinding  is  the  more 
accurate  as  it  prevents  inaccuracy  due  to  change  in  temperature  of 
the  piece  operated  on.  The  machine  must  be  amply  protected  from 
water  and  grit  in  wet  grinding  or  from  dry  grit  in  dry  grinding. 

429.  Grinding  Wheels. — Experience  has  shown  that  the  kind  of 
wheel,  its  periphery  speed,  the  extent  of  contact  between  the  wheel 
and  the  work,  and  the  rate  of  feed  of  the  wheel  over  the  work  are 
essential  factors  in  successful  grinding. 

The  kind  of  wheel  depends  upon  three  factors,  viz.,  (1)  the 
grinding  material  of  which  the  wheel  is  made;  (2)  the  size  of 
grains  of  this  material,  and  (3)  the  strength  of  the  cement  bond 
holding  the  grains  together.  Wheels  are  made  of  emery,  one  of  the 
many  forms  of  aluminum  oxide  found  in  nature;  corundum,  an 
artificially  made  aluminum  oxide  much  purer  than  emery;  and 
carborundum,  a  compound  of  silicon  and  carbon.  Corundum  and 
carborundum  are  products  of  the  electric  furnace.  These  materials 
are  crushed  to  powder,  and  the  grains  are  separated  according  to 
their  sizes.  A  wheel  is  made  up  by  mixing  grains  of  a  certain  size 
with  a  bonding  material.  Hydraulic  cement  is  much  used  for 
bonding  high-grade  wheels.  The  wet  mixture  of  cement  and  grind- 
ing material  is  moulded  to  shape  and  burned  into  a  bonded  mass 
in  a  furnace  at  high  temperature.  In  operation,  the  wheel  cuts 
by  contact  of  the  sharp  hard  particles  against  the  material  operated 
on,  and  as  these  particles  become  dull,  they  gradually  crumble  away 
from  the  bonding  material  and  give  place  to  sharper  particles.  The 
softness  or  hardness  of  a  wheel  depends  upon  the  strength  of  the 
bonding  cement. 

Makers  of  wheels  and  of  grinding  machines  supply  full  informa- 
tion of  the  proper  kind,  size  and  speed  of  wheel  for  each  class  of 
use. 

Wheel  surfaces  are  trued  by  a  diamond-pointed  tool  held  against 
the  wheel  as  it  revolves. 

430.  Lapping. — This  is  a  method  of  grinding  external  and  internal 
cylindrical  surfaces  to  a  finer  degree  of  accuracy    (-nrhnr  incn) 
than  can  be  obtained  with  certainty  in  the  use  of  a  grinding  wheel. 
It  is  under  more  certain  control  and  is  employed  to  finish  wheel- 


392 


MECHANICAL  PROCESSES 


ground  work  when  the  highest  attainable  degree   of   accuracy  is 
required. 

The  process  consists  of  revolving  the  work  in  a  grinding  lathe 
while  it  is  lightly  held  in  a  lead-lined  clamp  on  which  is  smeared 
a  thin  coating  of  oil  and  very  fine  grains  of  grinding  material. 
For  internal  grinding,  a  lead-covered  iron  plug,  or  a  plug  with  lead 
ribs  cast  in  longitudinal  grooves,  is  used  to  carry  the  grinding 
material.  The  hard  grains  of  grinding  material  become  unbedded 
in  the  soft  lead  and  their  grinding  action  is  guided  by  the  contact 
of  the  lead  itself  with  the  surface  to  be  ground. 


J__ III 


I    .   I 


/      \  ,    /      \   ,    / 

^'M'ERg 


i  .  i 


i.ii 


FIG.  268. — Armor  Plate  Hardening. 

431.  Armor-Plate  Making. — An  armor  plate  should  be  hard  enough 
on  the  outer  surface  to  prevent  penetration  by  a  shell  and  tough 
enough  under  the  hard  surface  to  resist  breaking  or  cracking. 
Armor  plate  is  commonly  made  of  nickel-steel  with  which  is  alloyed 
chromium,  tungsten,  or  vanadium.  Nickel  increases  toughness 
and  the  other  metal  increases  hardness. 

Armor  steel  is  made  from  high-grade  ore  by  either  the  acid  or 
the  basic  open-hearth  process.  The  reduction  of  phosphorus  in  the 
steel  is  highly  essential,  hence  the  basic  process  is  employed  in 
America.  The  ingot  is  cast  in  a  very  large  cast-iron  mould  lined 
inside  with  a  layer  of  hard-baked  loam.  It  is  forged  to  shape  under 


OTHER  SHOPS — SPECIAL  PROCESSES  393 

a  powerful  hydraulic  forging  press,  is  planed  to  dimensions,  and  is 
then  subjected  to  the  hardening  process. 

Fig.  268  shows  the  diagram  of  two  plates  prepared  for  hardening. 
A  heavy  steel  car  is  covered  with  layers  of  fire  brick  to  protect  it 
from  intense  heat,  and  on  this  is  built  the  structure  shown.  The 
flues  1,  2,  3,  4  allow  the  passage  of  hot  gases  under  the  lower  plate. 
Between  the  two  plates  is  a  layer  of  powdered  charcoal.  The  car 
supporting  this  structure  is  rolled  into  a  regenerative  furnace  and 
is  walled  in.  It  is  then  heated  up  gradually  and  kept  above  a  red 
heat  for  several  days.  The  carbon  penetrates  the  steel,  as  in  the 
cementation  process,  and  the  degree  of  penetration  depends  upon 
the  degree  of  heat  and  upon  the  length  of  time  the  heat  is  main- 
tained. It  is  estimated  that  the  process  occupies  five  days  for  heat- 
ing and  cooling  and  one  day  for  each  inch  of  penetration  of  the 
carbon.  As  carbon  is  absorbed,  the  angle  iron  frame  gives  down 
under  the  weight  of  the  upper  plate  and  allows  this  plate  to  remain 
it  contact  with  the  carbon. 

The  plates  are  hardened  after  removing  and  cleaning.  This  is 
done  by  reheating  and  spraying  the  carburized  surfaces  with  jets 
of  cold  water.  This  hardness  penetrates  only  about  2  inches  or  less, 
but  the  surface  is  so  hard  that  it  cannot  be  cut  or  drilled. 

The  processes  of  armor  making  are  guarded  with  much  secrecy 
by  the  few  manufacturers  who  are  engaged  in  this  work. 


APPENDIX 

432.  Table  of  Brasses  and  Bronzes. — The  following  table  gives  a 
list  of  the  brasses  and  bronzes  in  common  use.  Their  compositions  as 
here  given  are  more  or  less  varied  by  manufacturers. 

The  skill  of  melters,  and  their  personal  experience,,  lead  them  to 
good  results  on  alloys  with  mixtures  not  exactly  the  same  in  relative 
amounts. 


396 


APPENDIX 


a 


•sqi 


snaoqd 

o 


. 


0^3     g 

«       u 


•ou;Z 


8       S 


Muntz  Metal. 
Cast  Naval  B 


1       =3 


APPENDIX 


397 


433.  Degrees  of  Hardness  of  Steel  Tools. — The  amount  of  carbon 
in  various  well-known  tools  and  implements  made  of  hardened  steel 
is  shown  approximately  by  the  following  list: 


.6  to  .7  per  cent. 

.7  to  .8  per  cent. 

.8  to  .9  per  cent. 

.9  to  1.0  per  cent. 

Screw  drivers. 

Smiths'  hammers. 

Wrenches. 

Machinists' 

hammers. 

Anvil  tools. 

Punches  for  metals. 

Circular  saws. 

Hand  saws. 

Gun  barrels. 

Hand  picks. 

Lathe  centers. 

Cold  chisels. 

Chisels  for  hot 

Wood  augers. 

Anvil  facing. 

metals. 

Steel  springs 

Vise  jaws. 

for  Vehicles. 

Drop-forgingdies. 

1.1  to  1.2  per  cent. 

1.20  to  1.26  per  cent. 

1.26  to  1.30  per  cent. 

1.30  to  1.50  per  cent. 

Rock  drills. 

Pocket  knives. 

Ball  bearings. 

Saws  for  cut- 

ting steel. 

Threading  taps 

Wood  chisels. 

Strong  magnets. 

and  dies. 

Tools  for  cutting 

Hatchets,  axes. 

Files. 

hard  metals. 

Lathe  tools. 

Twist  drills. 

Wire-drawing 

Metal  scrapers. 

Steel  springs 

dies. 

for  power. 

Pipe  cutters. 

Glass-cutters. 

Milling  cutters. 

Cutters  for  wood- 

working machines. 

Degree  of 
Hardness. 


Per  cent 
of  carbon. 

Very  hard   1.50 

Hard 1.25 

Medium  hard 1.00 

Tough 80 

Tenacious 65 

Very  elastic 30 

434.  File  Making. — To  illustrate  many  of  the  essential  opera- 
tions in  making  tools,  a  description  of  file  making  is  here  given. 
This  description  applies  to  a  flat  tapered  file  of  rectangular  cross 
section.    The  steel  used  is  a  superior  grade  of  high-carbon  crucible 
26 


398  APPENDIX 

steel,  received  from  the  manufacturers  in  bars  about  12  feet  long 
and  of  the  same  cross  section  as  the  file.    The  steps  are  as  follows : 

(1)  Forging. — A  bar  is  cut  into  blanks  of  the  length  required. 
Each  blank  is  heated,  the  tang  or  handle  end  is  forged  by  a  rapidly 
working  machine  hammer,  and  the  taper  end  is  forged  by  hand. 

(2)  Annealing. — As   the   blanks    cool,   they   become   somewhat 
hardened  and  must  be  softened  by  annealing.    Several  forged  blanks 
are  packed  in  a  bulky  cast-iron  box,  and  its  lid  is  placed  on  and 
luted  with  clay.     Small  blanks  lose  some  carbon  in  heating  for 
forging,  and  this  is  restored  by  packing  carbon  around  the  blanks 
to  be  annealed.    The  cast-iron  boxes  and  contents  are  heated  gradu- 
ally in  a  furnace  to  red  heat  and  allowed  to  cool  slowly,  occupying 
two  or  three  days. 

(3)  Straightening. — When  annealed,  the  blanks  are  inspected  by 
a  man  who  straightens  crooked  blanks  by  tapping  with  a  hammer. 

(4)  Grinding  and  Draw  filing. — Straightened  blanks  are  ground 
on  large  grind  stones  to  remove  scale  and  expose  a  clean  metal  sur- 
face.    Some  blanks  are  so  ground  as  to  remove  entirely  any  de- 
carburized  surface  due  to  heating  before  forging.     The  grinding 
is  in  some  cases  supplemented  by  filing  the  blanks  to  make  them 
level  across  their  length,  as  the  stones  cannot  grind  a  true  flat 
surface. 

(5)  Cutting. — The  teeth  are  then  cut  on  the  blanks  in  a  machine. 
A  blank  lies  flat  on  the  lead-covered  machine  table  and  is  fed  in  the 
direction  of  its  length  under  a  wide  chisel  which  is  held  by  the 
machine  and  made  to  oscillate  rapidly  in  a  vertical  direction  or  in 
a  direction  slightly  inclined  to  the  vertical.    This  chisel  strikes  the 
blank  and  cuts  a  gash  entirely  across  its  width.    A  double-cut  file 
is  run  under  this  chisel  twice  before  the  opposite  side  of  the  blank 
is  cut.     A  rasp  file  is  cut  by  a  small  chisel  resembling  a  punch 
which  strikes  the  blank  at  an  angle  and  raises  teeth  from  its  sur- 
face.    If  the  blank  is  bent  in  cutting  the  teeth,  it  is  straightened 
by  a  lead  hammer.     This  is  seldom  necessary. 

(6)  Dipping. — After  cutting,  the  files  are  usually  stamped  with 
the  name  of  the  makers,  and  are  then  prepared  for  hardening  by 
dipping  into  a  mixture  which  forms  a  film  over  the  surface  and 
prevents  oxidation  of  the  tooth  points  as  the  file  is  passed  from  the 
heating  to  the  hardening  bath.     If  necessary,  this  dipping  is  pre- 
ceded by  a  bath  of  strong  alkali  to  remove  grease. 


APPENDIX 


399 


(7)  Heating  and  Hardening. — Each  pile  is  then  heated  gradually 
by  dipping  it  into  a  molten-lead  bath  kept  at  a  uniform  high-tem- 
perature by  oil  burners.    It  is  hardened  and  tempered  in  one  opera- 
tion by  quenching  in  salt  water. 

(8)  Cleaning. — After  hardening,  each  file  is  cleaned  by  scrub- 
bing, and  is  further  relieved  of  dirt  and  clinging  particles  of  metal 
by  subjecting  it  for  a  moment  to  a  blast  of  fine  sand  and  water. 
This  renders  the  teeth  clean  and  sharp. 

(9)  Softening  Tangs. — The  tang  ends   (handle  ends)   are  then 
softened  by  heating  in  lead  and  cooling  in  oil.    This  keeps  the  tang 
from  breaking  when  in  use. 

(10)  Final  Inspection — Testing. — Each  file  is  now  carefully  ex- 
amined for  defects  in  manufacture,  and  if  perfect,  is  oiled  to  pre- 
vent rusting.     It  is  then  struck  on  an  anvil  to  detect  from  the 
sound  any  possible  flaw,  and  is  tried  in  filing  a  piece  of  metal  of 
standard  hardness  to  discover  if  it  has  the  right  hardness.    If  these 
tests  are  passed,  the  file  is  brushed  and  sent  to  the  packing  and 
shipping  department. 

435.  Wire  Gage  Table. — The  following  table  is  given  to  show  a 
comparison  of  the  various  wire  gage  systems : 


Actual  Dimensions  in  Fractions  of  an  Inch. 

Wire 

4" 

5 

Gage 
Units. 

American  or 
Brown  <fe 
Sharpe. 

Birmingham 
Wire  Gage 
or 
Stubb's  Iron. 

Stubb's  Steel 
Wire. 

U.  S.  Standard 
for  Steel  and 
Iron  Plates. 

British 
Imperial 
Standard 
Wire  Gage. 
(S.  W.  G.) 

0000 

.4600 

.454 

.406 

.400 

000 

.40964 

.425 

.... 

.375 

.372 

00 

.3648 

.38 

.... 

.344 

.348 

0 

.32486 

.34 

.313 

.324 

I 

.2893 

.30 

.227 

.281 

.300 

2 

.25763 

.284 

.219 

.266 

.276 

3 

.22942 

.259 

.212 

.250 

.252 

4 

.20431 

.238 

.207 

.234 

.232 

5 

.18194 

.22 

.204 

.219 

.212 

10 

.10189 

.134 

.191 

.141 

.128 

20 

.03196 

.035 

.161 

.0375 

.036 

30 

.01002 

.012 

.127 

.0125 

.0124 

40 

.00314 

.... 

.097 



.0048 

50 



.069 

.001 

Intermediate  sizes  above  No.  5  are  not  here  given. 


400  APPENDIX 

436.  Wire  Dies. — Wire  dies  are  usually  made  of  chilled  white 
cast  iron,  hard-carbon  steel,  and  alloy  steel.     The  very  smallest 
sizes  of  dies  are  made  of  diamonds  because  drawing  soon  enlarges 
a  very  small  hole  in  a  steel  die. 

Sometimes  a  coil  of  wire  is  found  in  the  market  which  is  not  of 
the  same  size  throughout.  This  may  be  due  to  running  the  draw- 
ing block  too  fast,  which  stretches  the  wire  in  soft  places  after  it 
has  passed  through  the  die,  or  it  may  be  due  to  the  wearing  of  the 
die.  When  it  is  essential  that  a  coil  of  wire  be  of  the  same  diameter 
at  both  ends,  it  is  drawn  nearly  to  gage  in  a  roughing  die  and  is 
finished  in  another  die  which  has  little  work  to  do. 

As  diamond  is  the  hardest  substance  known,  it  requires  special 
means  and  considerable  time  to  get  a  hole  in  a  diamond  die.  An 
uncut  gem,  somewhat  flat  and  round,  is  mounted  in  a  piece  of  soft 
metal  and  is  firmly  secured  in  a  small  machine  much  resembling  an 
ordinary  sewing  machine.  The  oscillating  arm  of  this  machine 
carries  a  small  hard  steel  point,  just  as  a  needle  is  carried  in  a  sew- 
ing machine,  and  the  arm  is  adjusted  to  make  this  point  strike  the 
diamond  surface  just  at  the  end  of  the  oscillation.  The  point 
strikes  the  diamond  several  hundred  times  a  minute  and  a  cutting 
action  is  obtained  by  covering  the  gem  with  diamond  dust  held  in 
place  by  oil.  The  steel  point  is  revolved  as  it  oscillates,  and  it  is 
so  worn  at  the  end  of  10  or  15  minutes  that  it  is  replaced  by 
another  point.  It  requires  a  week  or  more  to  cut  a  very  small  hole 
in  the  diamond.  Steel  points  are  ground  round  by  holding  them 
against  a  diamond  chuck  revolved  rapidly  by  a  small  lathe. 

437.  Dimensions  of  Standard  Iron  Pipes. — The  following  table 
shows  the  standard  dimensions  of  iron  pipe,  including  standard 
threads  for  ends  of  the;  pipe.     These  standard  sizes  are  made  in 
wrought  iron,  mild  steel,  and  brass  as  commercial  products. 

In  ordering  iron  pipe  it  is  necessary  to  designate  only  the  size 
of  pipe  required  as  given  in  the  first  column  of  the  table,  without 
any  mention  of  thickness. 


APPENDIX 


401 


Actual 

Actual 

Size 

Outside 

Thickness 

Threads 

Size 

Outside 

Thickness 

Threads 

Inches. 

Diameter 

Inches. 

per  Inch. 

Inches. 

Diameter 

Inches. 

per  Inch. 

Inches. 

Inches. 

X 

.405 

.068 

27 

3K 

4.0 

.226 

8 

\/ 

.54 

.088 

18 

4 

4.5 

.237 

8 

% 

.675 

.091 

18 

4K 

5.0 

.246 

8 

y* 

.84 

.109 

14 

5 

5.563 

.259 

8 

% 

1.05 

.113 

14 

6 

6.625 

.280 

8 

i 

1.815 

.134 

ll/^ 

7 

7.625 

.301 

8 

\% 

1.66 

.140 

UK 

8 

8.625 

.322 

8 

\% 

1.9 

.145 

HM 

9 

9  .  625 

.344 

8 

2 

2.375 

.154 

UK 

10 

10.75 

.366 

8 

2K 

2  .  875 

.204 

8 

11 

11.75 

.375 

8 

3 

3.5 

.217 

8 

12 

12.75 

.375 

8 

438.  Methods  of  Threading  Bolts. — Bolts  are  usually  threaded  by 
being  held  firmly  in  a  machine  which  runs  a  briskly  revolving  thread- 
ing die  along  the  body  of  the  bolt  as  far  as  the  thread  is  to  extend. 
These  dies  are  kept  deluged  with  oil  while  they  work,  though  the 
work  is  so  severe  that  they  wear  out  rapidly. 

A  very  effective  thread  for  the  cheaper-made  bolts  is  either  cold 
or  hot  pressed  on  the  bolt  by  a  machine,  the  essential  principle  of 
which  is  shown  in  Fig.  269.  The  bolt  B  is  placed  between  the  flat 


i_£— : 

I -jzz* — 


f=/afr 
FIG.  269. — Dies  for  Rolling  Threads  on  Bolt  Ends. 

dies  C  and  D  which  are  made  to  move  in  the  direction  of  the  arrows 
and  are  held  firmly  at  a  given  distance  aj>art  by  bearing  against  the 
parallel  faces  of  the  guides  F  and  G.  Each  die  moves  forward  and 
back  once,  traveling  a  distance  in  one  direction  equal  to  at  least 
the  circumference  of  the  bolt. 

The  side  view  of  the  die  plate  shows  how  it  is  cut  to  impress 
threads  on  the  bolt.  The  notch  N  is  cut  in  the  face  of  the  die  to 
the  depth  of  the  threads. 


402  APPENDIX 

439.  Illustration  of  Automatic  Screw  Machine  Work. — Fig.  270 
shows  the   steps  in  the  work   of   cutting  the   small   helical   gear 
wheel  shown  at  W  in  Fig.  92,  Chap.  VI.     This  is  done  in  six 
operations,  requiring  a  total  of  80  seconds  of  time.     A  dimen- 
sion drawing  of  the  wheel  is  shown  at  the  bottom  of  the  illustration. 
Operation  IV,  that  of  cutting  the  spiral  teeth,  is.  done  by  a  very 
ingenious  tool  made  up  of  several  moving  parts,  all  automatically 
operated,  and  designed  at  the  works  of  The  Brown  &  Sharpe  Mfg. 
Co.,  Providence,  R.  I. 

440.  Shop  Location  and  Equipment. — In  locating  and  equipping 
a  manufacturing  plant  the   following-named   factors   are   of   im- 
portance : 

(1)  The   cost   of   obtaining   raw   materials   at   their   source   of 
supply,  their  quality  and  the  available  quantity. 

(2)  Cost  of  transporting  raw  materials  to  the  plant  and  finished 
products  to  market. 

(3)  Cost  of  fuel  for  manufacturing. 

(4)  Cost  and  available  supply  of  labor  needed. 

(5)  All  buildings  should  be  well  lighted,  dry  and  comfortable 
and  convenient  for  workmen. 

(6)  The  power  house  (boilers,  engines,  and  electric  generators) 
should  be  located  convenient  for  receiving  fuel  and  for  distributing 
power  to  the  shops  needing  it. 

(7)  The  buildings  should  be  so  located  with  reference  to  one 
another  as  to  afford  a  short  and  ready  means  of  transferring  work 
from  one  shop  to  another  in  regular  course  of  construction. 

(8)  Appliances  for  lifting  and  carrying  heavy  work  readily  in 
the  shops  should  be  installed,  and  the  machines  in  each  shop  should 
be  placed  to  reduce  necessary  handling  of  heavy  work  to  a  mini- 
mum. 

From  the  receiving  of  raw  materials  at  a  plant  until  they  leave 
as  finished  products,  they  are  handled  many  times.  It  saves  time, 
labor,  and  cost  to  reduce  this  handling  to  a  minimum,  and  careful 
study  should  be  made  with  the  view  of  eliminating  all  unnecessary 
handling.  Much  unnecessary  handling  and  many  needless  move- 
ments of  workmen  are  many  times  overlooked  because  they  are  a 
part  of  custom  or  habit.  These  points  are  given  careful  attention 
in  progressive  shops. 


APPENDIX 


403 


FIG.  270.— Specimen  Operation  of  Automatic  Screw  Machine. 


404 


APPENDIX 


441.  Allowance  for  Forcing  and  Shrinkage  Fits. — A  table  is  here 
given,  showing  the  usual  allowance  or  difference,  in  fractions  of  an 
inch,  between  a  shaft  and  the  hole  in  which  it  fits,  for  forcing 
and  shrinkage  fits. 


Shrinkage  fits. 


Forcing  fits. 


Diameter  in 
inches. 

Allowance  (or 
difference  in  di- 
ameters). 

Diameter  in 
inches. 

Minimum 
allowance. 

Maximum 
allowance. 

2 

.0025 

2 

.003 

.005 

8 

.0090 

8 

.009 

.011 

16 

.0175 

16 

.014 

.017 

40 

.0400 

65 

.0700 

442.  IT.  S.  Standard  Screw  Threads. 


Diameter  of 
screw. 

Threads  per 
inch. 

Diameter  at 
root  of  thread. 

Diameter  of 
screw. 

Threads  per 
inch. 

Diameter  at 
root  of  thread. 

\ 

20 

.185 

2 

4V2 

1.7113 

sg 

18 

.2403 

21/4 

4^ 

1.9613 

k 

16 

.2936 

2i/2 

4 

2.1752 

7 

14 

.3447 

2% 

4 

2.4252 

3/2 

13 

.4001 

3 

Sifc 

2.6288 

9 

12 

.4542 

3V4 

31/2 

2.8788 

% 

11 

.5069 

££ 

3V4 

3.1003 

3/4 

10 

.6201 

3% 

3 

3.3170 

7/3 

9 

.7307 

4 

3 

3.5670 

1 

8 

.8376 

4V4 

27/8 

3.7982 

Hfe 

7 

.9394 

4V2 

2% 

4.0276 

1*4 

7 

1.0644 

434 

2% 

4.2551 

1% 

6 

1.1585 

5 

2^ 

4.4804 

H/2 

6 

1.2835 

514 

£% 

4.7304 

1% 

5V2 

1.3888 

5V2 

2% 

4.9530 

1% 

5 

1.4902 

5% 

2% 

5.2030 

1% 

5 

1.6152 

6 

2*4 

5.4226 

443.  Hydraulic  Data. 


TABLE  OF  GALLONS. 


Cu.  ins.  in  a 
gallon. 

Wt.  of  gal., 
pounds 
avoirdupois. 

Gallons  in 
a  cu.  ft. 

One  cu.  ft.  of   water  at 
its   maximum  density, 
39.1°     Fahr.,    weighs 
62.425  Ibs.    avoirdupois. 

United  States.... 
Imperial  

231 

277.274 

8.33 
10.00 

7.480 
6.242 

APPENDIX  405 

One  Imperial  gallon =  1.2  U.  S.  gallons. 

One  U.  S.  gallon =  0.833  Imperial  gallon. 

268.8  U.  S.  gallons  of  water =  1  ton. 

35.88  cubic  feet  of  water =  1  ton. 

1  cubic  inch  of  water =  .03613  pound. 

Cubic  feet  of  water  x  62.425 =  pounds. 

Cubic  inches  of  water  x  .03613 =  pounds. 

U.  S.  gallons  x  .13368 —  cubic  feet. 

Cubic  inches  x  .004329 =  U.  S.  gallons. 

Cubic  feet  x  7.48 =  U.  S.  gallons. 

Cubic  inches  x  .0005787 =  cubic  feet. 

Pressure    of    a    water    column    in 

pounds  per  square  inch —  height  of  column  in  feet  x  .4335. 

Pressure    of    a    water    column    in 

pounds  per  square  foot =  height  of  column  in  feet  x  62.425. 

One  cu.  ft.  sea  water  at  62°  Fahr.  .=  64  pounds. 
One  cu.  in.  sea  water =  0.037037  pounds. 


INDEX 


A  PAGE. 

Abrasive  materials 330 

Absorption  point 150 

Accuracy  of  surface  grinding,  390 

Accurate  cutting  of  holes 322 

Acetylene  gas  for  welding  ....  384 

Acid  ores   40-41 

Acid  process  of  steel  making. .     89 
Adjustments  of  machine  bear- 
ings     283 

Alcohol  as  fuel 64 

Alcohol,  sources 63 

Allowance      for      forcing      or 

shrinkage  fits 404 

Allowance  for  shrinkage,  pat- 
tern making 218 

Alloy  of  magnesium 20 

Alloys  17 

Alloys,  peculiarities  of 17-18 

Alloys,  requirements    of    pre- 
paring       18 

Alloys,  table  of   395-396 

Alloys,  used     for     machinery 

parts    395-396 

Alloys,  well    known    designa- 
tions of 18 

Alloy  steels    113-114 

Alloy  steels,  uses  of 113-114 

Alloy  steel  tools,  hardening  of,  270 

Alumina    51,  57 

Aluminum  bronze    19 

Aluminum,  fusing  point  of . .  24 
Aluminum,  production  of. ...  57 
Aluminum,  properties  of  ....  24 

Aluminum,  sources  of 57 

Aluminum,  strength  of 24 

Aluminum,  uses  of 23 


PAGE 

Aluminum,  welding  and  sold- 
ering     386 

Annealing  15,  151-152 

Annealing  in  blacksmith  shop,  270 
Annealing  of  boiler  plates  . . .  352 
Annealing  of  brass  and  copper 

work    369-370 

Annealing  of  sheet  brass  ....  155 
Annealing  of  sheet  copper  . . .  154 
Annealing  of  sheet  iron  ....  161 
Annealing  of  steel  castings, 

152,  258 
Annealing  of  steel  forgings..    152 

Anti-friction  metal 20 

Antimony    24 

Anvil  for  blacksmithing  ....     262 

Anvil  tools    264 

Appliances  for  steam  hammer 

forging    271-273 

Architectural  shapes 130,  157 

Armor  plate,  cutting  of 387 

Armor  plate,  manufacture  of,  392 

Ash  and  refuse  in  fuel 59 

Autogeneous  welding 389 

Automatic  screw  machine.  .196-197 
Automatic  screw  machine,  work 

of 198,  402,  403 

Automobile   forgings    192-195 

B 

Band  saw   211 

Basic  ores   40-41 

Basic  process  of  steel  making,  89 

Bauxite   51-52,  57 

Beading  boiler  tubes 358 

Bearing,  meaning  of 323 


408 


INDEX 


PAGE 

Bearings,  adjustment  of 283 

Bench  equipment,  machine 

shop    323 

Bench  work,   machine  shop..   323 

Bending  slab 374-375 

Bessemer  converter    92 

Bessemer  converter,  operation 

of    93 

Bessemer  process 89,  91-92 

Bessemer  process,  features  of,     96 

Bessemer  steel,  uses  of 96 

Beton    25 

Billet    124 

Billet  mill    135 

Billets  for  forgings 261 

Blacksmith  anvil    262 

Blacksmith  forge    262 

Blacksmith  tools    263-264   ' 

Blast  furnace    37-40 

Blast  furnace,  fusion  zone  . .  45 
Blast  furnace,  modifications  of,  40 
Blast  furnace,  operation  of  42-45 

Blast  main     39 

Blast  stoves    45-48 

Blister  copper 54 

Blister  steel    90 

Blooming  mill   128,  131-133 

Blooms  and  billets 124-125 

Blooms  and  billets,  reheating 

of    139-142 

Blooms  for  forgings    261 

Blooms,  wrought   iron    83 

"  Blowing  in  "  a  blast-furnace,  42 
"  Blowing  out  "  a  blast-furnace,  45 

Blow  pipe    384-385 

Blow  pipe  cutting  of  metals. .   387 

Blow  pipe  welding 384-386 

Boiler     building,     assembling 

parts  353 

Boiler  drums,  welding  of,  386-387 
Boiler,  laying  out  parts  . .  340-341 

Boiler  material   339 

Boiler  plates,  annealing 352 

Boiler  plates,  bending   344-345 


PAGE 

Boiler  plates,  cleaning    342 

Boiler  plates,  drilling  holes..   352 
Boiler  plates,  flanging. 347-349,  351 

Boiler  plates,  laying  out   342 

Boiler  plates,  planing     edges, 

343-344 

Boiler  plates,  shaping    343 

Boiler  riveting   354-355 

Boiler  rivets  " 196,  362 

Boiler  shop  equipment 359 

Boiler  steel    340 

Boiler  tube  expander    357 

Boiler  tubes,  making  of  ...  171-176 
Boiler  tubes,  means  of  fasten- 
ing       357 

Boilers,  types   of    338 

Bolt  making   195-196 

Bolts,  methods  of  threading  ..401 
Bolts,  types  and  sizes   ....334-336 

Boring 300,  314-316 

Boring  bar   294-295,  331 

Boring  deep  holes 322 

Boring  machine  (for  wood) . .  213 
Boring  machines    (metal)    313-316 

Boshes 39 

Brass 18-19,  396 

Brass,  annealing  sheets  of   . .   155 

Brass,  extruded    155-157 

Brass,  furnace  for  melting,  250-251 
Brass,  general     methods     o  f 

shaping    125 

Brass,  rolling  of  sheets 155 

Brass,  table    giving    composi- 
tion     395-396 

Brazing    368-369 

Brazing  cast  iron  389 

Brazing  forge    369 

Brazing-metal    368 

Breaking  down  forgings 191 

Breaking  down  ingots 125 

Briquettes   63 

British  Thermal  Unit    (B.  T. 

U.)     59 

Brittleness    ,  15 


INDEX 


409 


PAGE 

Brittleness  of  unannealed  steel,  152 

Bronze 18,  19-20 

Bronze,    general    methods    of 

shaping    125 

Bronze,  rolling  of  sheets 155 

Bronze,  table  giving  composi- 
tion        396 

Building  and  repairing,  shops 

for    199-200 

Burned  steel 151 

Burning  on   387-389 

B.  W.  G.  (wire  gage)   166 

B  &  S.  (wire  gage)  166 


Calcination  of  iron  ores 69 

Calcination  of  ores 36 

Calipers 281,  284,  285,  286-287 

Carbon  in  iron  and  steel  .  .70,  74-75 

Carbon  in  steel  tools 397 

Carborundum    330,  391 

Cartridge  cases,  pressing  of  . .   186 

Case  hardening   376-377 

Casting  pit 103-105 

Castings,  defects  in    251-252 

Castings,  remedies  for  defects,  252 
Castings,  repair  of,  380-381,  386-389 
Castings,  steel.  (See  Steel 

castings.) 
Castings,  Thermit  process  of 

making 381 

Cast  iron  70 

Cast  iron,  brazing  of   389 

Cast  iron,  carbon  in   74 

Cast  iron,  expansion    in   cool- 
ing       250 

Cast  iron,  fusing  point    77 

Cast  iron,  properties  of 77 

Caulking  boiler  work   358 

Caulking,  tools  for 358 

Cement    24-25 

Cement,  Portland.     (See   also 

Portland  Cement.)    24 

Cement,  quick-setting 25 


PAGE 

Cements,  causes  of  setting 29 

Cements  for  metals 378-379 

Cementation  process    90 

Cementation  process,      discov- 
ery of  88 

Center  punch  281 

Centering  work  for  lathe  ....  296 
Change  in  shape  of  new  cast- 
ings       321 

Changes  in  properties  of  metals    15 
Changes  in  steel  due  to  heat- 
ing       150 

Chaplets    242 

Charcoal 60 

Charcoal  iron    71 

Chasers  for  screw  threads. . . .  300 

Chemical  laboratory 200 

Chill  moulds   242-243 

Chrome  steel 114 

Chromite   51 

Chuck,  drill    303 

Chuck,  lathe    292-293 

Chuck,  planer    306 

Chuck  and  porter  bar 148-149 

Chuck  stub   148 

Circular  saw,  setting  teeth  . .   214 

Circular  saw  table  206 

Classification  of  forces 16 

Clay 51 

Coal    60 

Coal,  desirability  of    59 

Coal,  powdered    62 

Coal  screenings  63 

Coating  for  wire 167 

Cogging  mill 131,  132-133 

Coke  and  coke-making   61-62 

Coke  furnace  61 

Cold-blast  iron  71 

Cold  chisels    324 

Cold  pressing  of  sheet  metals 

185-189 
Cold  pressing  of  sheet  metals, 

examples 187,  188,  189 

Cold  rolled  steel  .  .  144 


410 


INDEX 


PAGE 

Cold-short  iron    76 

Cold  shuts  in  ingots  and  cast- 
ings    119,  252 

Colors  for  judging  hardness  of 

tools    269 

Combined  carbon  in  iron  . . .  .74,  77 

Combustion     58 

Composition    (alloy)    18 

Compression  16 

Concentration  of  iron  ores 68 

Concrete    25 

Concrete,  method  of  using  ..28-29 
Concrete,  proportions  of  mix- 
tures      28 

Concrete,  re-enforced 27 

Concrete,  water  proof  qualities    29 

Conductivity    15 

Continuous  mill 132 

Converter,  Bessemer    92 

Converter,  for  copper 53 

Converter,  Tropenas    257 

Cope    219,    230 

Copper,  annealing  of 21 

Copper  converter    53 

Copper,  fusing  point  of 21 

Copper,  general     methods     of 

shaping    125 

Copper,  how  disposed  of  from 

smelter    123 

Copper,  impurity  allowable  in 

sheet  153 

Copper,  impurities  in 21 

Copper,  native  35 

Copper  pipe   and   pipe   joints, 

371-373 
Copper  pipe,  shaping  of  . .  365- 

368,  371-372,  377-378 

Copper,  production  of   52-55 

Copper,  properties  of 21 

Copper  refining 54-55 

Copper,  rolling  into  sheets   . .  153 

Copper  shop  equipment 364 

Copper,  sources  of 52 

Copper,  strength  of 21 

Copper,  uses  of 20 


PAGE 
Core  boxes  and  core  prints. . . .  222 

Cores  for  moulds 241 

Corrugated   iron    160 

Corundum     391 

Countersink    303 

Cracks  in  forgings 323 

Critical  points  150 

Crocus  cloth  330 

Crop  ends  of  steel 118,  148 

Crucible  process    107-108 

Crucibles    109 

Crucibles,  method  of  charging,  111 

Crucible  steel    90 

Crucible  steel,  expense  of  ....  107 
Crucible  steel  furnace  ....109-111 
Crucible  steel,  materials  of  . .  108 
Crucible  steel,  properties  of  .  112 

Crude  petroleum 63 

Cupola    247 

Cupola,  operation  of  248 

Cuts  in  woodworking 216 

Cutting  holes  with  blowpipe.  387 
Cutting  metals  with  blowpipe,  387 
Cutting  of  metals,  speeds  for.  276 
Cutting  of  screw  threads.  .297-300 

Cutting  speed  of  tools   321 

Cylinders  for  gas  storage 185 

D 

Defective    castings,    remedies 

for   252 

Defects  in  castings    ..251-252,   259 

Defects  in  steel  ingots 118-119 

Defects  in  rolled  metals 143 

Defects  in  seamless  tubes 181 

Degree  of  heat  for  forging,  266,  274 
Degrees  of  hardness  from  car- 
bon       397 

Degrees  of  hardness   in   steel 

tools    397 

Degrees  of  refinement  in  ma- 
chining   276,  282-283 

Density    15 

Diamond  cutting  for  wire  dies,  400 
Dies,  for  cutting  threads,  326-328 


INDEX 


411 


PAGE 

Differential  pulley   331 

Direct  metal 71 

Discard  in  steel  ingots 118 

Dividers   281 

Dolomite    51 

Dote,  in  lumber 33 

Draft  of  patterns  219 

Drag  (moulding) 219,  230 

Drawing-blocks  (wire  mak- 
ing)    165 

Drawing  or  drafting  room,  200-201 

Drawing    out  (forging) 266 

Drawings  for  shop  use 201 

Drawings,  methods  of  repre- 
senting by  201-202 

Drawings,      orthographic   and 

isometric 202,  203 

Drawings,  purpose  of   200 

Drawing  wire .164-166 

Drawing  wire,  dies  for 400 

Drilling  holes,  methods  of  ...  300 
Drilling  machines,  types  of  . .  300 
Drilling  machines,  for  boiler 

shop 353 

Drills,  types  of   303 

Driving  fit 283 

Drop  forging  automobile  parts, 

192-193 
Drop  forging,  dies  for,  191-192-193 

Drop  forging  hammer   190-191 

Drop  forging,  largest    195 

Drop  forging  operations    ..191-193 

Drop  forgings    189 

Drop  forgings,  specimens,    194-195 

Drop  forgings,  utility  of   261 

Dry  process  of  smelting 36 

Ductility    15 

Duplex  process 106 

Durability  of  wood 34 

B 

Effects  of  hammering  and  roll- 
ing metals  144 

Effects  of  hydraulic  forging 
press  145 


PAGE 

Effects  of  rolling  metals 142 

Effects  of  steam  hammer,  145,  274 

Elastic   limit    16 

Elasticity 15 

Electric  current  for  welding,   380 

Electric  steel  furnace 122 

Electric  welding 379-381 

Electricity  in  Metallurgy 57 

Electrolysis  in  copper  refining, 

54,  55 

Elongation 16 

Emery 330,  391 

Engineering  materials    ......     14 

Equipment  for  bench  work  . .  323 

Erecting  shop   200-275 

Essential  features  of  patterns,  218 
Essential  factors  in  hardening 

steel    152 

Essentials    in    machine    shop 

work   276 

Example     of     making     small 

mould    239-240 

Examples  of  patterns 220-221 

Examples  of  work,    automatic 

screw  cutting  machine 198 

Extruded    brass    and    bronze, 

155-156 
Extruded   shapes    157 

F 

Face  plate 292 

Factors  in  hardening  steel  . . .   152 

Fatigue  of  metals 15-16 

Ferro-manganese 77 

Ferro-silicon   75 

Fettling   81 

Files,  manufacture  of 397-399 

Files,  varieties  of 324-326 

Fillets 222-223,  322 

Fins  138,  143 

Fire  bricks   52 

Fire  clay   51,  234 

Fitting  by  forcing    404 

Fitting  by  shrinking 404 

Fittings  for  pipes   332-334 


412 


INDEX 


PAGE 

Fixed  carbon  in  coal 60 

Flange  heating  furnace 351 

Flanging  mild  steel  plates,  347-348 

Fluid  compressed  steel 119-122 

Fluxes  for  soldering 371 

Flux  for  brazing 368 

Flux  for  smelting 41-42 

Flux  for  welding 267 

Fluxing  mixture  for  galvaniz- 
ing       162 

Forces,  classification  of 16 

Forcing  fit 283 

Forcing  presses 320 

Forge     equipment     for     hand 

work    261-262 

Forge,  essentials  for  heating,  265 

Forge  for  brazing    369 

Forge  shop   260 

Forge  shop  equipment    271 

Forging  appliances  for  steam 

hammer 271-273 

Forgings,  drop.       (See     Drop 
forgings.) 

Forgings,  large    145 

Forgings,  materials  for   261 

Forgings,  measuring  stock  for,  267 

Forging  terms  266 

Forms     of     newly     produced 

metals    123 

Forms  of  screw  threads 299 

Foundries,     iron,     steel,     and 

brass   228,  253 

Foundry  cupola 247 

Foundry  cupola,  operation  of,  248 

Foundry  equipment 231 

Foundry  iron  249 

Fuel,  ash  and  refuse  in 59 

Fuel,  components  of 59 

Fuel,  essentials  for  burning  . .     58 
Fuel  for  blacksmith  forges  . .  265 

Fuel  for  producer  gas    67 

Fuel,  heating  value  of 59 

Fuels,  classes  of  59 

Fuels,  liquid    63-64 


PAGE 

Fuels,  objections      in      metal- 
lurgy         58 

Fuel,  uses   58 

Fuller  bar  272 

Furnace,  annealing 152,  258 

Furnace,  blast    37 

Furnace,  electric,  for  steel...   122 
Furnace  for     heating     flange 

work  351 

Furnace  for  lieating  rivets   . .   356 
Furnace  for  melting  brass  . . .  250 

Furnace,  open  hearth 97-99 

Furnace,  open  hearth,    charg- 
ing     99-100 

Furnace,  puddling 80-81 

Furnaces    for   steam-hammer 

work   273 

Furnaces,  muffle 152 

Furnaces,  reheating    140-142 

Furnaces,  reverberatory,   37,   48-50 

Furnaces,  smelting 37 

Fusibility 15 


Gage,  depth 284 

Gage,  drill    285 

Gage,  fixed    285 

Gage  for  metal  thicknesses,  166-167 
Gage  for  pipe  and  tube  walls,  167 

Gage,  surface 282 

Gage,  wire  and  sheet  metal  . .  285 
Gages,  inside  measuring  .  .284,  287 

Gaging  sizes  of  wire 166 

Galvanized  iron 160 

Galvanizing   161-162 

Gang  drills  302 

Gangue 35 

Ganister 51 

Gas  carbon  in  coal 60 

Gas  fuels    64 

Gas,  natural   64 

Gas  producer    64-65 

Gas  storage  cylinders 185 

Grinding,  accuracy  of,  390,  391,  392 


INDEX 


413 


PAGE 

Grinding  accurate  surfaces  . . .   390 

Grinding  machines 390 

Grinding  wheels    391 

H 

Hammers,  blacksmith   263 

Hand  planer 212 

Hand  tools,  woodworking    . . .  214 

Handling  large  forgings 148 

Hard  solder   368 

Hardening  baths  for  steel,  159,  270 

Hardening  of  alloy  steel    270 

Hardening  of  steel   152,  159 

Hardening  of  steel  tools    269 

Hardest  steel  known 114 

Hardness   15 

Hardness  of  tools,  judging  by 

colors    269 

Hardwood  lumber    31 

Hardwood  lumber  grades 32 

Heartwood    31-32 

Hearth  of  smelting  furnace  ...     39 
Hearth  of  puddling  furnace  . .     81 

Heating  in  a  forge 265 

Heating  of  steel,  methods 159 

Heat  treatment  of  metals 149 

Heterogeneous  welding 389 

High  carbon  steel  74,  79,  91 

Highest  degree  of  surface  ac- 
curacy       390 

High-speed  steel 113,  114 

Holders-on  for  riveting   355 

Hole  cutting  by  blow  pipe 387 

Hot  blast  main  39 

Hot  short  iron 75 

Hydraulic  accumulator    . . .  349-351 

Hydraulic  data 404-405 

Hydraulic  flanging  press  .  .348-349 
Hydraulic  forging  press   ..145-148 
Hydraulic  forging  press,      ef- 
fect of   145 

Hydraulic  lime 25 

Hydraulic  riveting  machines ..   355 

Hydraulic  shears    128 

Hydrogen  gas  for  welding  . . .  384 
27 


I  PAGE 

Illuminating  gas 67 

Impurities  in  ores 35 

Impurities  in  steel   117-118 

Impurity    allowable    in    sheet 

copper    153 

Influence  of  quenching  in  hard- 
ening tools 270 

Ingot    124 

Ingot  moulds    114-116 

Ingots,  defects   in    118 

Ingots,  heating  necessary  for 

rolling 128,  129 

Ingots,  method  of  rolling  .  .128-129 
Ingots,  reducing     to     smaller 

form    125 

Ingots,  reheating  of 126-127 

Ingots,  stripping  from  moulds,  117 

Inspecting  department   200 

Inspection  of  rolled  material,  142 
Inspection  of    material.     (See 
Defects.) 

Iron,  charcoal    71 

Iron,  chemically  pure  73 

Iron,  classified      methods     of 

shaping    124 

Iron,  cold  blast 71 

Iron  for  foundry  use   249 

Iron,  general  classes  of 74 

Iron,  grey,  mottled  and  white,  249 
Iron,  how    disposed    of    from 

smelter  123 

Iron,  ingredients  entering  mol- 
ten   70,  74-77 

Iron  ores  68 

Iron  ores,  preparation      for 

smelting   68-69 

Iron  ores,  reduction 70 

Iron  pipe,     standard     dimen- 
sions     400-401 

Iron,  pig,  converted  into  steel,  123 
Iron.    (See  also  Steel,  pig  iron, 
cast  iron,  wrought  iron,  mal- 
leable iron.) 
Isometric  method  of  drawing,  202 


414 


INDEX 


J  PAGE 

Jacks  for  lifting 331 

Jacks  for  planer  work 306 

Jigs    304 

Joining  metals,  methods  of  . .  378 

Jointer    . 212 

Joints  for  copper  pipe 372-373 

Joints    in  woodworking 216 

Journal    ,  .   323 


Ladles  for  foundry  use 249 

Ladles  for  steel 104 

Ladles  shanks   112 

Lapping  (grinding) 391-392 

Large  forgings    145 

Large  forgings,  handling  of  . .   148 

Lathe  attachments   292 

Lathe  boring  bar 294 

Lathe  chucks 292-293 

Lathe  dog   289 

Lathe  mandrels    293-294 

Lathes,  examples  of  woodwork 

in  208 

Lathes  for  metal  working,  207, 

287-291 

Lathes  for  wookworking,    207-210 
Lathes,  hand  tools  for  wood- 
working      209 

Lathes,   how   sizes  are  desig- 
nated       209 

Lathe,  steady  rest 296 

Lathes,  swing  of 209 

Lathe  tools    (for  metals),  291-292 

Lathe  work,  centering 296 

Laying-down  board 224 

Leaching   36 

Lead  pipe 157 

Lead,  properties  of 23 

Lead,  smelting  of 56 

Lead,  sources  of  56 

Lead,  uses  of 23 

Lifting  jacks 331 

Lime 25 

Lime,  hydraulic 25 


PAGE 

Limestone  in  ores 40 

Limestone,  use  in  steelmaking,  100 

Liquation    18 

Liquid  fuels 63-64 

Loam  for  moulding 234 

Looping  mill    132 

Lumber,  dressed   33 

Lumber,  grading  of 31 

Lumber,  hard  and  soft  wood. .  31 
Lumber  inspection  rules  . . .  .32-33 

Lumber,  log  run  31 

Lumber  measurement  34 

Lumber,  methods  of  sawing. .     30 

Lumber,  quarter    sawed    30-31 

Lumber,  shakes  in 33 

Lumber,  standard  defects  ...  33 
Lumber,  standard  lengths  ...  32 
Lumber,  standard  thicknesses,  32 

M 

Machining  278 

Machine  screws    334-336 

Machines  for  cold  pressing  of 

metals    186 

Machines   for   cutting  screws, 

196-198 
Machine  shop  equipment,    276-278 

Machine  shop  notes   321 

Machine  shop  practice  ....275-276 
Machine  shop  work,  degrees 

of  refinement  in  ...  .276,  282-283 

Machine  tools 278,  287 

Magnesia  in  ores 40 

Magnesite    51 

Magnesium  alloy 20 

Malleability    15 

Malleable  Iron    78,   376 

Malleable  iron,    processes    o  f 

making    375-376 

Mandrels  for  lathe  work  ..293-294 

Manganese  bronze    19 

Manganese  in  iron   70,  76 

Manganese  steel 114 

Manganese  steel,  hardening  of,  153 


INDEX 


415 


TAGE 

Marking  a  plate  for  flanging  . .   346 

Marking-off  table 224,  279-280 

Marking  work  for  machining, 

278-279 

Materials  for  forgings    261 

Materials  for  patterns 215 

Materials  of  construction  ....     14 

Materials,  properties  of 14-15 

Matte  (copper  smelting)    53 

Measuring  stock  for  forgings,  267 
Melting  brass  for  castings,  250-251 
Melting  iron  for  castings,  247-248 

Merchant  bar  131 

Merchant  mills    131 

Metal  cements 378-379 

Metal-cutting  saws  320 

Metal   scrapers    329 

Metallurgy,  electricity  in 57 

Metals,  annealing  of 151-152 

Metals,  cold  pressing  and  shap- 
ing    185 

Metals,  effect  of  rolling 142 

Metals,  extraction  of 36-45 

Metals,  fatigue  of 15-16 

Metals,  forms  when  newly  pro- 
duced     123 

Metals,  heat  treatment  of  ...  149 

Metals,  main  sources  of 35 

Metals,  mechanical    treatment 

of 144 

Metals,  re-manufacture  of  ....  158 

Micrometer  caliper 286 

Mild  steel  74,  79 

Mill  scale    130 

Milling  machine    308-311 

Milling  machine  attachments, 

312-313 

Milling  machine  cutters 313 

Mineral  oil  63 

Mixer    71 

Mortise  machine  213 

Mould,  example  of  loam  ..243-246 
Mould,  example  of  making  . .  239 
Mould,  parts  of 219 


PAGE 

Mould  loft  floor 200 

Moulds,  classes  of 228 

Moulds,  dry  sand 229 

Moulds,  essential  features  of,  231 
Moulds  for  chilled  castings, 

242-243 

Moulds  for  steel  castings 254 

Moulds  for  steel  ingots  ..114-116 
Moulds,  green  sand,  228-229, 

230-231 

Moulds,  loam 228,  229,  243-246 

Moulds,  open  sand 228,  229-230 

Moulders'  tools 238-239 

Moulding  accessories 237 

Moulding  flasks  235-237 

Moulding  machines  241 

Moulding  materials 234-235 

Moulding  sands  233-234 

Muck  bar 85 

Muffle  furnaces  152 

Multiple  spindle  drills 302 

N 

Nail  making 195 

Native  copper 35 

Natural  gas 64 

"  Neat  "  cement 28 

Necking  tool 272 

Neutral  axis  17 

Nickel,  properties  and  uses..  23 
Nickel,  sources  and  smelting,  56 

Nickel  steel 113,  261 

Notes  on  steam  hammer  forg- 
ing     274 

Nowell 219,  230 

Nuts ..196,  334-336 


Oil  tempering    153 

Open  hearth  furnace  (steel)  .     97 
Open  hearth  furnace,  charg- 
ing    99-100 

Open  hearth  furnace,      opera- 
tion   ,  ..100-102 


416 


INDEX 


PAGE 

Open  hearth  furnace,  tapping 

out 102 

Open  hearth  process    96 

Open  hearth  steel,  uses  of 106 

Ores    35 

Ores,  acid  and  basic 40-41 

Ores,  impurities  in 35 

Ores,  iron.     (See  Iron  ores.) 

Ores,  treatment  of    35-36 

Orthographic  method  of  draw- 
ing      202 

Oxidizing  atmosphere 50 

Oxy-acetylene  blow  pipe 331 

Oxygen  for  blow-pipe  use 384 


Parting  sand 234 

Pattern   maker,    requirements 

of  205 

Pattern  shop 205 

Pattern  shop  accessories    224 

Pattern  shop  equipment    205 

Pattern  shop  power  tools 205 

Patterns,  drawing      from 

moulds    219-221 

Patterns,  essential  features  of,  218 

Patterns,  examples*  of 220-221 

Patterns,  materials  used  for  . .  215 
Patterns,  methods  of  marking,  223 

Patterns,  records  of 224 

Patterns,  varieties  of 225 

Peculiarities  of  alloys   17-18 

Pene  (shape  of  hammers) 263 

Permanent  set 16 

Phosphor  bronze  19 

Phosphorus  in  iron 70,  76 

Phosphorus  in  smelting  flux  .     42 

Pig  boiling 82 

Pig  iron.     (See  also  Iron.)   ..70-71 
Pig  iron,  grades  of,  how  pro- 
duced         73 

Pig  iron,  grey,     mottled     and 

white  73,  249 

Pig  iron,  inspection    of    frac- 
ture .  73 


PAGE 

Pig  iron,  substances  contained 

in  70 

Pig  iron,  tests  for  purchase  . .     73 
Pipe  bending    methods,     367, 

371-372,  377-378 

Pipe,  butt  welded   168-169 

Pipe,  cast  iron    168 

Pipe,  commercial-iron   171 

Pipe  cutting  and  threading  ma- 
chine       319 

Pipe,  defects  in  welded 171 

Pipe,  extra  strong 172 

Pipe  fitting  332 

Pipe  fittings    332-334 

Pipe  fitting  tools   334,  335 

Pipe,  lap  welded 169-171 

Pipe,  manufacture  of  welded  .   168 

Pipe,  material  for  welded 168 

Pipe,  test  for  welded 171 

Pipe  threading 319 

Pipe,  welding  of 386 

Pipes.     (See  also  Tubes.)   ....   168 

Piping  in  steel  ingots 118 

Pitch  of  rivets 342 

Pitch  of  threads   298 

Pits 143 

Planer  (machine  shop)    ...304-305 

Planer,  parts  of .304-305 

Planer  tools  (metal  work)  ...   306 
Planer  (woodworking)   ...212-213 

Planished  iron 160,  164 

Planished  sheet  copper 155 

Plate  and  angle  shop 374 

Plate  mill    137 

Plates  of  iron,  largest  rolled,  137 

Pneumatic  tools    331 

Poling  process  of  refining  cop- 
per         54 

Portable  tools  330-331 

Porter  bar 148-149 

Portland  cement 24-25 

Portland  cement.      (See    also 
Cement.    See  also  Concrete.) 
Portland  cement,  composition 
of    ..25-26 


INDEX 


417 


PAGE 

Portland  cement,  effect  of  clay 

and  lime  in   26 

Portland  cement,  improved  in 

storage  26 

Portland  cement,  manufacture 

of    26-27 

Portland  cement,  uses  of 27 

Power  tools  (machine  shop) . .  287 
Precautions  in  heating  steel  . .  142 

Producer  gas  64-66 

Producer  gas,  constituents  of, 

66-67 

Producer  gas,  fuel  for  making,  67 
Propeller  blades,  planing  of  .  306 
Propeller  blades,  moulding  in 

foundry    307 

Properties  of  materials   14-15 

Properties  of     materials, 

changes  in 15 

Protective  coating  for  wire  . . .  167 

Protractor   285 

Puddle  balls  83 

Puddle  bar    85 

Puddle  rolls    84 

Puddling  furnace 80-81 

Puddling  (repair  of  castings),  389 
Puddling  (wrought  iron  mak- 
ing)     80-81 

Pull-over  mill 132,  154 

Punch,  hand 361 

Punch,  power    361 

Q 

Quarter  sawed  lumber 30-31 

Quenching  baths  for  hardening 

steel 159,  270 

Quick-setting  cement 25 


Radial  drilling  machines,  302-303 

Rail  mill  136 

Railroad  rails,  making 128, 137 

Ratchet  drill 330 

Reamers    .  .324 


PAGE 

Recalesence  point 150 

Red  short  iron 75 

Reducing  atmosphere   50 

Reduction    36 

Re-enforced  concrete   27 

Refractory  materials   50-52 

Reheating   blooms,    slabs   and 

billets    139-142 

Reheating,  furnaces  for   ..140-142 

Reheating  of  ingots 126-127 

Re-manufacture  of  metals  . . .   158 
Remedies    for   defective    cast- 
ings     252 

Reverberatory  furnaces   48-50 

Reverbera  tory    furnaces,      a  t- 

mosphere  of  50 

Reversible   mill,   128-129,   132, 

133-134 

Rivet  heating  furnace 356 

Rivet  holes  in  boiler  work  ...   352 

Rivet  making    195-196 

Rivets,  cutting  by  blow  pipe. .  387 

Rivets,  shapes  of   362 

Riveting  in  boiler  work 354 

Roasting   furnace    48-50 

Roasting  ores 36 

Roll  scale 130 

Rolled  material,  inspection  of,  142 

Rolling  angle  bars 138-139 

Rolling  mill  parts 137-138 

Rolling  mills,  types  of 86,  131 

Rolling  mill,  work  of 125 

Rules  for  lumber  inspection  . .     32 
Russia  iron 160,  164 


Sands  for  moulding 233-234 

Sap  wood  31-32 

Saw  table  (circular  saw)  206 

Saws  for  cutting  metals 320 

Scabs    143 

Scarfing  (in  forging)    266 

Scrapers  for  metals 329 

Screenings  of  coal  ....  63 


418 


INDEX 


PAGE 

Screw  cutting  machines 196 

Screw  cutting  machines,  work 

of 402,  403 

Screw  threads,  cutting    ...297-300 
Screw  threads,  definitions  ...   298 

Screw  threads,  forms  of 299 

Screw  threads,  standards  of. .   299 
Screw  threads,  U.  S.  standard,  404 

Scribers   281 

Segregation 118 

Self-hardening  steel 113,  114 

Sensitive  drill   302 

Set-screws   337 

Shapes  of  rivets 362 

Shaper    307 

Shearing    16 

Shears  for. metal  cutting  ....   361 

Shear  steel 90 

Sheet  bar*  mill 137 

Sheet  bars   131,  160 

Sheet  copper 153-155,  364 

Sheet  iron    and    its    manufac- 
ture     160-161 

Sheet  metal,  tools  for   364-367 

Sheet  metal  work    363 

Sheet  mills    131,  154 

Shop  drawings    201 

Shop  location  and  equipment,  402 
Shops  of  a  building  and  repair 

plant   199 

Shop  work,  consecutive  order 

of 202 

Shrinkage  allowances 218 

Shrinkage  cracks  in  steel  cast- 
ings     255 

Shrinkage  fit    283 

Shrinkage  rule    218 

Siemens  process  (steel  making)    89 

Siemens-Martin  process    89 

Silica,  acid  material  in  ores  .  .     40 
Silica,  refractory  material    . .     51 
Silicate  of  aluminum  in  ores. .     40 
Silicate  of  aluminum,   refrac- 
tory material 51 


PAGE 

Silicon  in  iron 70,  75 

Silicon  pig    75 

Sizes  of  standard  iron  pipe,  400-401 

Skelp 168 

Skelp  mill  137 

Slabbing  mill  131 

Slabs  (rolled  steel) 125 

Slabs,  reheating  of 139 

Slag,  blast  furnace 42 

Sliding  fit   283 

Slotting  machine   317 

Slotting  machine  tools   318 

Smelting    36 

Smelting  charge,  making  up. .     42 

Smelting,  furnaces  for   37 

Smelting  iron    70 

Smooth  cutting  of  metals  ....   321 

Snakes 143,  181 

Snapping  bar  272 

Soaking  pit   125-127 

Soft  wood  lumber 31 

Solder     370 

Soldering    370-371 

Soldering  fluxes 371 

Special  steels  113 

Speed  for  cutting  metals 276 

Spelter 22,  56,  368 

Spiegel-eisen   77 

Spinning  lathe 187 

Spinning,  shaping  metals   by, 

185,  187 
Spring  swage  (steam-hammer 

work)    273 

Springing  work  while  machin- 
ing     321 

Squeezer , 83-84 

Steady  rest  296 

Steam  hammer    271 

Steam  hammer  appliances,  271-273 
Steam  hammer,  effects  of,  145,  274 
Steam  hammer,  forging  notes,  274 

Steel  alloys 113-114 

Steel  alloys,  hardening  of,  153,  270 
Steel,  best  effect  in  annealing,  152 


INDEX 


419 


PAGE 

Steel,  burned    151 

Steel,  carbon  in 74 

Steel  casting  at  steel  works. .   124 

Steel  castings 253 

Steel  castings,  annealing,  152,  258 
Steel  castings,  avoiding  shrink- 
age cracks 255 

Steel  castings,  defects  in 259 

Steel  castings,  material  for  . .  256 
Steel  castings,  moulds  for. . . .  254 
Steel  castings,  reshaping  b  y 

forging 261 

Steel  castings,  temperature  of 

pouring    258 

Steel  castings,  welding  of  ...  386 
Steel,  changes  due  to  heating,  150 
Steel,  classified  methods  of 

shaping    124 

Steel,  cold  rolled 144 

Steel,  crystals  affected  by  heat- 
ing       151 

Steel  cylinders  for  gas  storage,  185 
Steel,  effects  of   alloying  ma- 
terials on  heating 151 

Steel,  effects  of  rolling 142 

Steel,  fluid  compressed 119-121 

Steel  for  boilers     340 

Steel  forgings,    annealing 152 

Steel>  forms  of  newly  produced,  123 

Steel  foundry 253 

Steel  furnace,  electric 122 

Steel,  grades  of,  how  classed,  78-79 

Steel,  hardest  known 114 

Steel,  heating  and   hardening 

of  159 

Steel,  hardening  of 152 

Steel,  history  of  88 

Steel,  impurities  in 117-118 

Steel  ingots,  defects  in 118-119 

Steel  ingots,  moulds  for  ..114-116 

Steel  ingots,  record  of   144 

Steel,  ladle  for 104 

Steel  made  bad  by  treatment,  142 
Steel  making,    Bessemer    pro- 
'     cess    .  ..91-93 


PAGE 

Steel  making,  cementation  pro- 
cess        90 

Steel  making,  crucible      p  r  o- 

cess    107 

Steel  making,  duplex  process,  106 
Steel  making,  open  hearth  pro- 
cess     96-97 

Steel  making,  origin  of  basic 

process   89 

Steel  making,  outline   of  pro- 
cesses         91 

Steel  making  processes,  dates 

of 88,  89 

Steel  making,  Talbot  process, 

105-106 
Steel  moulds,  essentials  of  . .  254 

Steel  moulds,  surfaces  of 254 

Steel,  necessary  heat  for  shap- 
ing     151 

Steel,  oil  tempering 150 

Steel,  pouring  of 94-96,  105 

Steel,  precautions  in  reheating,  142 

Steel,  properties  of 78-79 

Steel,  simple  test  for 79 

Steel,  size  of  crystals 78 

Steel  tools,  hardness  of 397 

Steel,  uses  of  open  hearth 106 

Steel.   (See  also  Mild  steel,  al- 
loy steel,  high  carbon  steel.) 

Stoves,  blast  furnace 45-48 

Straight-edge    281 

Strength  of  welded  joints,  379,  387 
Stripping  ingots  from  moulds,  117 

Structural  mill 134 

Structural  shapes,   cutting  by 

blow  pipe    387 

Structural  shapes,  extruded..    157 

Structural  shapes,  rolled    130 

Sulphur  in  iron 70,  75 

Surface  cracks  in  forgings  . . .   323 

Surface  gage    282 

Surface  plates 329-330 

Swage  block 265 

Swaging 266 


420 


INDEX 


T  PAGE 

Talbot  process  of  steel  making, 

105-106 
Tangential  cuts  of  lumber  ..30-31 

Taps  and  dies 326-328 

Temperature  for  forging,  266,  274 
Temperature  for  pouring  steel 

castings    258 

Tempering  steel  tools 269 

Tensile  strength 16 

Tension    16 

Terne  plates 164 

Testing  room  200 

Thermit  process,  features  of. .  381 

Thermit  process,  uses  of 382 

Thermit  welding   382-384 

Thread  cutting  by  hand  ..326-328 
Threads.  (See  Screw  threads.) 

Threading  bolts 401 

Three-high  mill 132,  135 

Tilting  crucible  steel 113 

Timbers,  sawing  of 30 

Tin   (metal)    22-23,123 

Tin  (metal)  sources  of 56 

Tin  (tin  plate) 160 

Tin  plate,  manufacture  of,  162-164 

Tin  plate,  qualities  of 164 

Tin  plate,  standard  size    163 

Tinning    162 

Tinsmith  tools  364-366 

Tool  making 158-159 

Tools,  essential  features  of. .  159 
Tools  for  blacksmithing  ..261-265 
Tools  for  bench  work  on 

metals 323 

Tools  for  caulking     boiler 

seams    358 

Tools  for  hand  lathe 209 

Tools  for  lathe 291-292 

Tools  for  marking-off  table, 

280-282 

Tools  for  measuring 283-286 

Tools  for  moulding    238-239 

Tools  for  pipe  fitting 334,  335 

Tools  for  planer    306 


PAGE 
Tools  for  slotting  machine  ...   318 

Tools,  hardness  of 397 

Tools,  materials  of  158-159 

Tools,  power  for  machine  shop,  287 

Torsion    16 

Tropenas  converter  for  steel,  257 

Tube  expander,  boiler 357 

Tube-piercing  mills 173,  180 

Tubes.   (See  also  Pipes.)    ....  168 

Tubes,  brass  and  copper 180 

Tubes,  cold  drawn 177-179 

Tubes,  defects  in  seamless   . .  181 

Tubes,  hot  drawn   182-185 

Tubes,  hot  drawn,  example  of 

size 185 

Tubes,  making  of  seamless,  172-184 

Tubes,  seamless    172 

Tubes,  small 181 

Tubes,  thin-walled    181 

Tubes,  welded  and  seamless  . .  168 
Tungsten  steel,  hardening  of,  153 

Tuyeres,  blast  furnace 39 

Types  of  screw  threads 299 

U 
Uncombined  carbon  in  iron  . .     77 

Universal  rolling  mill 132,  134 

Upsetting  (forging)   266 

Uses  of  alloy  steels  113-114 

Uses  of  Bessemer  steel 96 

Uses  of  crucible  steel 107 

Uses  of  open  hearth  steel....  106 


Valve  re-seating  machine 331 

Vertical    boring    and    turning 

mill    315 

Vertical  drilling  machine  ....  301 

W 

Wane  (lumber  defect)  33 

Warping  of  wood 223 

Water  gas  67 


INDEX 


421 


PAGE 

Water  gas,  use  in  welding  . . .  387 

Welds,  types  of 268 

Welding  by  blow  pipe 384-386 

Welding  by  hand    267 

Welding  by  Thermit    process, 

381-384 

Welding,  electric   379-381 

Welding  methods  classified  . .  389 

Welding  of  steel  pipes  386 

Welding,  reducing  strength  of 

iron  379 

Wet    processes    of    extracting 

metals    36 

Wheels  for  grinding 391 

Whitworth    compressed    steel, 

119-122 

Wire-bar  (or  billets)   164 

Wire,  coating  for  protection  of,  167 

Wire   dies    165,  400 

Wire  drawing  bench  165 

Wire  for  springs 167 

Wire  gage  units    166,  399 

Wire,  hard    167 

Wire,  manufacture  of 164-166 

Wire,  material  for 166 

Wire,  method  of  coating 167 

Wire   ribbon    167 

Wire,  smallest  drawn 167 

Wire,  soft   168 

Wire,  tempering  of  167 

Wood  .as  fuel  .  60 


PAGE 

Wood,  durability  of 34 

Wood,  heart  and  sap 31-32 

Wood  trimmer 215 

Wood  used  for  patterns 215 

Wood,  uses  in  machinery 29 

Woodworking,  cuts  and  joints 

in  216 

Working  fit 283 

Wreckage,  cutting  up  by  blow 

pipe 387 

Wrenches,  types  of 328 

Wrought  iron,  advantages    of,     78 

Wrought  iron,  carbon  in 74 

Wrought   iron,    disadvantages 

of 78 

Wrought  iron,  history  of 79 

Wrought  iron,  manufacture 

of,  79-88 

Wrought  iron,  methods  of  pro- 
ducing       80 

Wrought  iron,  properties  of,  77-78 
Wrought    iron,  simple  test  for,    79 


Zinc,  impurities  in   22 

Zinc,  manufacture  of  ...55-56,  123 

Zinc  pot,  for  galvanizing  ....  162 

Zinc,  properties  of 22 

Zinc  protectors    21 

Zinc,  sources  of 55 

Zinc,  uses  of  ....  21 


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